US 3007542 A
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Description (OCR text may contain errors)
Nov. 7, 1961 s. w. GIAMPAPA ETAL 3,007,542
DEGASIFIER 5 Sheets-Sheet 1 Filed June 18, 1957 INYENTORS.
S'aZz/al'ore M 6: am
BY Zeaccra Ib A 1961 s. w. GIAMPAPA ETA). 3,007,542
DEGASIFIER Filed June 18, 1957 3 Sheets-Sheet 2 INVENTORS. Sela/alone M G-a'ampayw lemma 21o A. Haerzw Nov. 7, 1961 s.- w. GIAMPAPA ETAI. 3,007,542
DEGASIFIER 3 Sheets-Sheet 3 Filed June 18, 1957 INVENTORS SaZMzZare MG-Zzmpapo BY [ewe/ab A. flaw-Z2 WW Att'v.
United States Patent Ofiice Italy) Filed June 18, 1957, Ser. No. 666,307 4 Claims. (Cl. 183 -2.5)
This invention relates to devices for removing air and air components from aqueous liquids. Specifically, the invention provides such devices suitable for use in a paper mill to degasify paper stock immediately upstream of a papermaking machine.
7 The devices of the present invention comprise an elongated tube including end portions tapering-toward a relatively narrow middle portion. The liquid to be degasified is introduced tangentially into one end portion and is discharged in a tangential direction from the other end. While flowing from one end portion to the other, the liquid follows a helical path along the tube wall, the center of the tube being free from liquid. Each end portion of the tube is provided with an axial connection to a vacuum pump.
In this device, the liquid is firstraccelerated, then allowed to flow atincreased speed for a limited time, and thereafter decelerated. Thus, the pressure within the liquid is initially reduced and then maintained at a reduced value, which brings about generation of gas bubbles from gas dissolved in the liquid. These bubbles are driven by centripetal force into the hollow gaseous core along with whatever bubbles may have been present in the liquid before the liquid is introduced into the degasifying device. Such previously existing bubbles may have been floating freely in the liquid or may have been adhering to particles suspended therein, for example, cellulose fibers.
Special provisions are made for insuring the delivery of the degasified liquid in the form of a steadily flowing stream having substantially uniform velocity and pressure throughout its cross sectional area.
A centrifugal separator may be interposed between the degasifying device and the vacuum pump associated therewith, to recover droplets of liquid and also solid particles, such as cellulose fibers, suspended in the air flowing from the degasifying device.
The degasifying device of the present invention can be inserted into or made part of any closed pipe system. Very little space is required. Head loss is kept at a minimum. The only other additional equipment needed is a vacuum pump and, if desired, a separator.
In a paper mill, a degasifying device according to the present invention can be installed directly ahead of the paper forming machine, no additional pump being required.
Other and further features of the present invention will become apparent from the following description and appended claims as illustrated by the accompanying drawings which show, by way of examples, apparatus according to the present invention, and in which drawings:
FIGURE 1 is a side elevation of a degasifying device according to the present invention;
FIGURE 2 is a cross section taken along the line 2--2 of FIGURE 1;
FIGURE 3 is a cross section taken along the line 3-3 of FIGURE 1; V
FIGURE 4 is an exploded side elevation of a header, a helical header insert and a vacuum connection forming the top of the device of FIGURE 1;
FIGURE 5 is an exploded side elevation of a header, two inserts for said header and a vacuum conenction to- 3,007,542 Patented Nov. 7, 1961 gether forming the lower end of the device of FIGURE 1; and
FIGURE 6 is a diagrammatic flow sheet of a paper stock system around the paper machine, including a degasifying device according to the present invention.
Referring now to FIGURES 1 to 5, a degasifying device according to the present invention is there indicated generally by the reference numeral 10. As shown, this device includes a tubular member comprising an upper converging conical section 12 formed with a radial flange 14 at its upper end, a middle cylindrical section 16 and a lower diverging section 18 formed with a radial flange 20 at its lower end. A cylindrical tubular inlet header 22 is provided with upper and lowerradial flanges indicated at 24 and 26. The latter flange is seated on the flange 14 and removably held thereon by bolts 28. The header 22 comprises a tangential inlet conduit 30 provided at its distant end with a radial flange 32 adapted for connection to a flanged conduit. The inlet conduit 30 is round at its distant end, thereafter gradually changes into rectangular cross sectional shape and tapers toward its junction with the tubular header portion. The inlet conduit 30 extends at an angle of less than to the header 22.
Within the header 22there is disposed a cast insert 34 having an upper radial flange 36 seated on the flange 24 and extending short of the edge of the latter flange. The insert '34 is generally cylindrical and fits inside the header 22. A central axial conduit 38 extends through the insert 36 and is continued downwardly to the bottom of the insert 36 by a tube '40 integral therewith. The bottom surface of the insert 36 is formed as a helix 42 extending around the conduit 38 and tube 40. The helix 42 begins at the junction of the inlet conduit 30 with the header 22 and, specifically, at the upper corner of this junction and extends clockwise therefrom over 270 and terminates at the level of the lower corner of the junction of the inlet 30 with the header 22. The remaining 90 of the bottom surface of the insert 22 indicated at 44 extends upwardly along a streamlined configuration to a vertical surface 45 extending from the lower edge of the helix 42.
The top of the header 22 is closed by a round plate 46 of the same diametrical width as the upper header flange 24 and connected thereto by bolts 48, the flange 36 of the insert 34 being clamped between the flange 24 and the plate 46. A curved conduit 50 serves to connect the conduit 38 with a vacuum pump.
At the lower end of the degasifier an outlet header 52 is provided having a radial flange 54 facing the flange 20 of the degasifier tube and connected to the flange 20 by bolts 56. The outlet header 52 is generally cylindrical and tubular, having an inner diameter greater than the outer diameter of the lower end of the diverging degasifier tube section 18 and its outside close to the edge of the flange 54. On the inner surface of the outlet header there is formed a circumferential groove 57 having an upper wall surface '58 extending at a constant level and a lower wallsurface 60 extending helically therebelow from a point closely spaced from the surface 58 where the two surfaces '58 and 60 are connected by a vertical wall 62. The groove 57 defines a diverging circumferential conduit on the inside of the header 52' per flange 70 narrower than the flanges 20 and 54 and clamped therebetween. The member 68 extends downwardly below the outlet header 52 and has its inner surface aligned with the inner surface of the converging degasifier tube section 18. At its lower end, the member 68 is screw threaded, to receive an internally screw threaded annular radial flange 72. The member 68 fits snugly and tightly within the outlet header 52. A circumferential groove 74 on the outside of the member 68 may have an O ring 76 seated therein, to prevent any possible leakage between the inside of the header 52 and the outside of the member 68. A series of channels 78 are formed through the member 68 which open into the groove 57 in the header 52. The top and bottom walls of these channels slope downwardly from their inner mar gins radially outwardly, and also downwardly in a clockwise circumferential direction. The side walls of the channels extend axially with respect to the member 68, with one side wall offset vertically with respect to the other as a result of the clockwise circumferential downward slope of the top and bottom walls. Further, the side walls of the channels are streamlined and extend more or less tangentially with respect to the inner surface of the tubular member 68. The partitions between the channels 78' taper inwardly or, in other words, the chan: nels diverge outwardly.
The channels 78'may be said to be portions of a spiral of a very small height, as compared with its diameter.
A solid cylindrical casting 80 fits tightly within the tubular member 68. The upper surface of the casting may extend level with the lowermost points of the channels 78. Preferably, but not necessarily, the upper surface may be formed with radially divergent wedge-like projections 82 having sloping surfaces forming inward continuations of the bottoms of the channels 78 and vertical surfaces aligned with the higher side walls of these channels. The casting 80 is formed with a lower radial flange 84 narrower than and seated on the flange 72. The casting is also formed with a central axial conduit 86 which is continued upwardly by a tube 88.
A vacuum conduit 90 has a-radial flange 91 seated on the flange 84 and connected to the flange 72 by bolts 92.
An elbow-shaped conduit 96- of rectangular cross section is connected to the end of the outlet conduit 64, as by means of bolts 98 connecting a radial flange on the elbow 96 seated on the flange 66. The elbow 96 is turned counterclockwise away from the outlet header 52.
For use in a paper mill, a device such as that described hereinabove may includetapering or conical sections 12 and 18 each 32 inches long and each tapering from a diameter of 7.2 inches to a diameter of 3.0 inches. The middle cylindrical section 16 may be 30 inches long. The walls of the tapering sections may extend at an angle to the axis of the tube ranging from about 3.5 to 5.5 say, around' l". Four or more channels 78 may be provided through the tubular member 68, depending on the size of the device.
In the assembly of the above described device, the flange 72 of the tubular member 68 is threaded onto the tubular member 68 after the outlet header flange 54 has been seated on the upper flange 70 of the tubular member 68.
The device described hereinabove functions as follows. The liquid to be degasified follows a helical downward path through the degasifier, rotating in clockwise direc tion. This helical flow is established in the inlet header 22. The conduit 30 slopes downwardly (in other words, joins the header 22 at an angle of less than 90 with respect to the vertical axis of the degasifier) so that the liquid enters the header 22 at an angle which carries it downwardly-past the'discharge orifice of the conduit 30 within the first turn of the helical flow. The helical surface 42 aids in establishing the helical flow and, together with the streamlined surface 44, prevents turbulence at the upper end of the header 22. The angle of the inlet conduit 30 to the header 22 also is such as to prevent turbulence and energy loss due to friction on the entry of the liquid into the header 22. In the absence of the above noted angular arrangement of the conduit 30 with respect to the header 22 and the helical surface of the insert 34, establishment of helical flow would be accompanied with considerable liquid turbulence and loss of head due to friction. The specific angle of the conduit 30 with respect to the header 22 will be so designed with respect to the contemplated pressure in the liquid entering the device that the liquid will follow a helical path clearing the outlet orifice of the conduit 30. The greater the liquid pressure, the greater will be the pitch of this helical path. In other words, at greater liquid pressures the turns of the helical path will be spread further apart.
As mentioned hereinabove, the speed of liquid flow is increased in the converging tubular section 12. This accelerated rate of flow is maintained in the middle cylindrical section 16. In the lower diverging tubular section, the speed of liquid flow is decreased to restore approximately the original speed which restores the static energy or pressure at the inlet.
The lower end of the device is so constructed as to convert the liquid flow from a helical path to straight line flow with uniform speed and pressure throughout the cross sectional area of the liquid being discharged from the degasifying device. Further, this conversion is effected without turbulence or setting up pulsations in the liquid. Turbulence would cause loss of head and pulsations would be highly undesirable where uniform delivery of liquid must be maintained, for example, in the delivery of paper stock to a paper making machine.
Specifically, the provision of a plurality of outlet channels 78 of streamlined configuration having inlet orifices distributed circumferentially of the interior of the tubular member 68 serves to discharge liquid constantly, uniformly and without turbulence or pulsations to the groove or conduit 57 in the outlet header 52. Note that the orifices of the channels 78 are so shaped and located, one following closely after another, so as to pick up evenly each succeeding stratum in the helically flowing liquid and then to deliver the same to the groove or. conduit 57 along the line of least resistance and friction. Further when delivered to the groove or conduit 57, the liquid enters the latter tangentially, so that there is very little friction or turbulence at this point. The groove or conduit 57 increases in capacity circumferentially, from its starting point to the outlet conduit 64. The latter extends tangentially and at an angle of less than 90 with respect to the vertical axis of the outlet header 52, so that here too there is no turbulence or loss of head due to friction. Finally, in the elbow 96 the liquid derived from the radially inner portion of the liquid flowing through the groove or conduit 57 is decelerated, to bringabou-t complete uniformity in speed and pressure throughout the cross sectional area of the liquid being discharged from the degasifying device. Particularly in the handling of paper stock, dead spots are avoided, since it is recognized that dead spots bring about agglomeration or flocculation of suspended cellulose fibers or at least may cause stratification or uneven distribution in the stock of cellulose fibers, which is highly undesirable.
From the foregoing it will be apparent that a liquid to be degasified can be passed through the present degasifying apparatus with very small loss in head or pressure. Consequently, no pump is required downstream of our degasifying device, which is a great advantage, since most, if not all pumps, particularly after use for some time, tend to suck in atmospheric air, which is thus bled into the liquid being pumped. Thus, a degasified liquid would be regasified on being passed through a pump.
The rate of helical flow is such in the above disclosed degasifying apparatus that a central axial gaseous core is maintained therein throughout its length. This central gaseous core is maintained under vacuum. The upper vacuum tube 40 projects into the converging tubular section 12 while the lower vacuum tube 88 projects into the lower converging tubular section 18, to establish and maintain the above noted vacuum.
In the converging tubular section 12, the liquid pressure is reduced to such an extent as to produce the above noted gaseous core. The gases dissolved in the liquid come out of solution in the form of bubbles while gas bubbles already present in the liquid in free form (floating or travelling by themselves) or in residual form (attached to solids in suspension) become enlarged. Due to the rapid rate of helical liquid flow, the bubbles are subjected to centripetal forces which drive the bubbles into the hollow central gaseous core, from which gases thus derived from the liquid are removed at both ends of the apparatus through the tubes 40 and 88, which extend centrally and axially in the apparatus. These centripetal forces also detach bubbles which may adhere to suspended solid particles such as cellulose fibers. This degasifying process is continued and completed in the middle cylindrical tubular section 16.
FIGURE 6 shows a paper stock system around the paper machine including a plurality of degasifying units 182 according to the present invention each formed with a valved liquid inlet 104 and a valved liquid outlet 106. A branched vacuum conduit 108 connects the units 102 through a centrifugal separator 110 with a vacuum pump 112. Reclaimed fiber and water move through a conduit 114 to a wire pit or vat bottom 116 receiving white water from a paper making machine 118 (Fourdrinier or cylinder). Clean paper stock under pressure flows from a metering device 120 through a conduit 122 and a fan pump 126 to the degasifier inlet conduits 104. White water flows through a conduit 128 into the conduit 122 for admixture with the clean raw paper stock. A conduit 130 including a white water valve 132 receives degasified white water-diluted raw stock from the degasifier outlet conduits 106 for direct discharge to the paper making machine 118.
Free, residual and dissolved gas in paper stock has a number of undesirable effects on the quality of the web or sheet made from such a stock, such as large inter-fiber voids, hard spots, false bonding" between fibers which easily breaks, and the like. These disadvatages are all eliminated by degasifying the stock according to the present invention.
The methods and apparatus of the present invention are also applicable for the degasification of other liquids than those mentioned herein, including liquids carrying solid particles in suspension.
Many details may be varied without departing from the principles of this invention and it is therefore not our intention to limit the scope of this patent but it is our intention to embrace such variations as fall within the scope of the appended claims.
1. A degasifying device comprising a tubular member closed at both ends and having a cylindrical middle portion, an end portion converging toward said middle portion and another end portion diverging from said middle portion, a tangential inlet conduit discharging into the wide end of said converging end portion, a tangential outlet connected to the wide end of said diverging end portion, and axial vacuum connections at both ends of said device, the wide end of said diverging tube portion being formed with a plurality of generally radial channels extending generally spirally, said device further comprising means defining a generally circular conduit extending around the Wide end of said diverging tube portion to receive the discharge from said channels, said tangential outlet conduit communicating with said circular conduit.
2. A degasifying device comprising a vertical tubular member having a cylindrical middle portion, an end portion converging toward said middle portion and another end portion diverging from said middle portion, an inlet header connected to the upper wide end of the converging end portion, a tangential inlet conduit connected to said inlet header and inclined inwardly toward the central axis of said tubular member and toward the middle portion thereof, an insert closing the end of said inlet header and formed with a helical surface coaxial with said inlet header and originating at the discharge orifice of said inlet conduit at the part of said orifice closest to the end of said inlet header, said insert being formed with a central axial conduit and having a tube connected thereto in alignment with said conduit and extending into the converging portion, a tubular member connected to and aligned with the wide end of said diverging tube portion, said tubular member being formed with a plurality of circumferentially distributed channels extending generally spirally therethrough, an outlet header disposed around said tubular member defining a circular conduit communicating with said channels, a tangential outlet communicating with said circular conduit, said circular conduit being closed upstream of the inlet of said outlet conduit and diverging downstream thereof, and a closure member for said tubular member extending between the end thereof and said channels, said closure member being formed with a central axial conduit and having a tube connected therewith in alignment with said conduit and extending into the diverging tube portion, said tangential outlet being inclined inwardly toward the central axis of said tubular member and towards the middle portion thereof.
3. A method of degasifying a liquid which comprises causing said liquid to flow along a helical path while accelerating said liquid and subjecting the interior of said helix to a vacuum, subsequently decelerating said liquid while keeping the liquid flowing in a helical path, thereafter subdividing said liquid into a plurality of spaced individual streams each flowing outwardly radially along a clearly defined spiral path and reuniting said streams and causing the liquid to flow along a circular path substantially surrounding said spiral paths, and finally along a path. curving away from the center of said circular path.
4. A degasifying device comprising an upstanding tubular member closed at both ends and including a cylindrical middle portion, an end portion converging toward said middle portion and another end portion diverging from said middle portion, said portions presenting an unbroken inside wall surface in said member, a sole tangential inlet conduit discharging into the wide end of said converging end portion, a sole tangential outlet connected to the wide end of said diverging end portion, said conduits being inclined inwardly toward the central axis of said tubular member and toward the middle portion thereof, and axial vacuum connections at both ends of the device.
References Cited in the tile of this patent UNITED STATES PATENTS 575,934 Prokupek Ian. 26, 1897 2,590,754 Cline Mar. 25, 1952 2,705,053 Morris Mar. 29, 1955 2,737,857 Lee Mar. 13, 1956 2,757,581 Freeman et al. Aug. 7, 1956 2,757,582 Freeman et 'al. Aug. 7, 1956 2,769,546 Fontein Nov. 6, 1956 2,816,490 Boadway et al. Dec. 17, 1957 2,849,930 Freeman et a1 Sept. 2, 1958 OTHER REFERENCES McGraw-Hill, Pulp and Paper Manufacture, vol. 3, (part 1 relied on) 1953.