US2642950A - Deaerating a suspension of cellulosic fibers - Google Patents

Description

June 23, 1953 c. L.ICLI.ARK ETAL 2,642,950 DEAERATING-A SUSPENSION OFQCELLULOSIC FIBERS Filed Nov 30, 1951 5 Sheets-Sheet l mvau'rons Carleton L. Clark Carlo Vicorio Cornelius J. Lyons James A. Smiih William W. Hickey W ATTORNEY June 23, 1953 c. L; CLARK ETAL 2,642,950

DEAERATING A SUSPENSION OF CELLULOSIC FIBERS Filed Nov. 50, 1951 3 Sheets-Sheet 2 Fi .3. I I

ATTORNEY June 23, 1.953

c. CLARK EI'AL DEAERATING A SUSPENSION 0F- CELLULOSICV'FIBERS Filed Nov. 30, 1951 :5 Sheets-Sheet :=s

INVENTORS Carleton L. Ciur k Carlo Vicorio Cornelius J Lyon James A. Smith BY -William W. Hickey ATTORNEY Patented June 23, 1953 DEAERATING A SUSPENSION OF CELLU- LOSIC FIBERS Carleton L. Clark, North Tarrytown, and. Carlo Vieario, New York, N. Y.; and Cornelius J. Lyons, Norwalk, Conn., and James A. Smith, Greenburgh, and William W. Hickey, Bronxville, N. Y., assignors to The Rotareaed Corporation, Bronxville, N. Y.

Application November 30, 1951, Serial No. 259,248

12 Claims.

This invention relates to the de-aeration of paper stock before it goes to the paper-making machine, or to such stock that is to be subsequently formed into sheets, boards, or the like. This invention is an improvement on that disclosed in the patent application of Clark and Vicario, Ser. No. 110,450, filed August 15, 1949, now Patent No. 2,614,656, issued October 21, 1952, owned by applicants assignee. In that application, the stock to be de-aerated is forced into a tank maintained at a particular subatmospheric pressure by being atomized by atomizing nozzles projecting the stock against an impingement plate within the tank. It was found that so many nozzles had to be used, and so many plates, that in order to get increased capacity of the de-aerator, the tank into which the stock was atomized had to be quite large, so one of the objects of this invention is to devise ways and means for putting more nozzles in smaller tanks while still maintaining high efiiciency of tie-aeration.

Another object of this invention is to find if possible the maximum quantity of stock that can be atomized into the tank per nozzle. Since the projection of the atomized spray of stock from the nozzle onto an impingement surface is important, it is another object of the invention to re-arrange the impingement surfaces to fit any re-arrangement of the atomizing nozzles.

In the removing of air from the tank and the atomized spray of stock therein by means of vacuum, it becomes important to minimize the quantity of suspended stock that gets into the pipe leading from the tank to the vacuumproducing device, so it is another object to devise ways and means for deflecting such stock away from the vacuum pipe by trapping such suspended stock particles, accumulating them, and leading them downwardly into the pool of de-aerated stock that is in the bottom section of the tank.

In such a de-aerating tank, it is imperative that there be no protuberances or projections on which falling atomized stock can cling and build up, because the stock must be continually returned quickly to submergence, so it is another object of this invention to devise ways and means whereby the nozzles used have no stockretaining surfaces and whereby the impingement plates are secured to the tank walls in a completely smooth manner.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present emheaders are connected.

2 bodiment is, therefore, illustrative and not restrictive, since the scope of the invention is defined in the appended claims rather'than by the description preceding them, and all changes that fall within the metes and bounds, or of equivalents of such metes and bounds, are, therefore, intended to be embraced by those claims.

In the drawings:

Fig. 1 is a perspective view illustrating semidiagrammatically an apparatus embodying the improvements of the present invention;

Fig. 2 is an end elevation partly broken away and partly in section illustrating the arrangement of the double orifice nozzles and the outlet with its protecting grid;

Fig. 3 is a plan view of the vacuum tank or de-aerator;

Fig. 4 is an enlarged perspective view partly in section of a portion of the vacuum tank or de-aerator, showing the double orifice nozzles, the impingement plates and the reinforcing and bracing members; 7

Fig. 5 is a detail view illustrating the means for plugging the weep holes back of the curved impingement plates;

Fig. 6 is a detail sectional view of one of the nozzle units, illustrating the hood thereof.

Fig. 7 is a side view of the vacuum tank or de-aerator.

The apparatus arrangement embodying the improvements of the present invention and shown semi-diagrammatically in Fig. 1 of the drawings, comprises an open supply tank or chest It currently supplied by conduits H or l2, or by both conduits operating simultaneously. The-supply tank or chest I6 is connected by an outlet gravitational feed conduit [3 with a white water or stock supply pipe it connected with any desirable source of supply and provided with a control valve 15 and leading to a mixing pump l5, but the supply tank or chest Iii may be supplied with stock as explained in the aforesaid application. The stock level in the supply tank may be maintained constant at a suitable height by controlling the feed thereto.

' The mixing pump lt'is connected by a conduit I! with a pair of laterally spaced horizontal stock inlet headers [8 located above and extending longitudinally of a vacuum tank or deaerator IS. The mixing pump may, of course, be connected to rotary screens open to the atmosphere, which screens discharge to an open trough to which the horizontal stock inlet .This covers use of this invention with paper machines using such screens, such as for making newsprint and fine paper. The vacuum tank or de-aerator is in the form of a horizontally extending drum and the headers I8, which extend substantially the entire length of the drum, are closed at one end and are connected at the other end with the conduit preferably by diverging branches 20 of said conduit I1.

Leading from the horizontal headers l8 are vertical branch conduits 2| extending downwardly from the headers l8 and terminating slightly above the top of the drum and connected at their lower ends with double orifice spray nozzles 22 extending through the top portion of the vacuum tank and through which stock is projected into the tank. The stock being introduced into the tank is projected onto the central and side imperforate impingement surfaces or plates 23 and 24 and collects in a pool at the bottom of the vacuum tank below the impingement plates and is withdrawn from the tank bottom through a sump 25 by means of a pump 26.

The degree of vacuum required according to the present invention is maintained in the tank by any suitable means for producing the critical high vacuum described in the Clark and Vicario patent application heretofore mentioned. Since the vacuum-producing means is well known and forms no part of this invention, those means are shown herein only symbolically by means such as vacuum pumps 21 and 28 operating in series in an exhaust conduit 29 with a check valve 30 in the by-pass around the second stage pumps and which opens when the pumps are initially started up to allow seal water from the first stage pump 21 to be discharged without passing through the second stage pump. As soon as the vacuum is established between the two stages, this check valve closes and remains so during operation. In cases where the temperature of the stock in the mill is low, a vacuum stage may be inserted between the tank and these pumps comprising a pre-im'ector barometric condenser with a drop leg, a steam ejector and a barometric after-condenser. The vacuum pumps and the control means may be arranged in any desired manner, as will be readily understood, and a vacuum gauge 3| is shown for indicating the degree of reduced pressure thus maintained in the vacuum tank IS in terms of inches of mercury.

The double orifice nozzles are constructedsubstantially the same as the atomizing spray nozzles disclosed in the aforesaid application, with the addition of a second outlet neck 32 which is arranged opposite and in alignment with the outlet neck 33. Each nozzle assembly is connected by a branch connection 34 with the lower end of one of the branch conduits 2| of one of the headers l8 and is composed of an inlet neck 35 and a substantially cylindrical body portion 36 into which the neck leads tangentially, and which body portion represents an internally unobstructed swirl chamber 31 having end walls 38. The outlet necks 32 and 33 extend outwardly from the central portions of the end walls of the cylindrical body portion of the nozzle unit which, as illustrated in Fig. 6, may be provided with a hood 39 arranged to cover the shoulder 40 formed by offsetting the inlet neck of the nozzle unit from the center of the cylindrical body portion to arrange the inlet neck tangentially of the swirl chamber 31. The hood consists of a substantially rectangular plate of sheet metal or other suitable material curved at the upper edge at 4| to fit the exterior of the inlet neck and provided at opposite sides with approximately triangular wings 42 which extend from the side edges of the body portion of the hood to opposite sides of the inlet neck. The downwardly sloping surface provided by the diagonally extending plate or hood 39 is disposed at such an angle that its pitch will prevent stock alighting upon it from clinging to it, and, therefore, any sprayed stock settling onto these hoods will readily slide down and oil? of them and fall into the pool at the bottom of the vacuum tank without collecting on the spray nozzles.

The double outlet nozzles spraying in opposite directions handle a greater quantity of stock in a vacuum tank of a known size than a single nozzle. More volume cannot be handled through a single spray nozzle because any additional volume will spoil the spray pattern and would result in a stream of stock instead of a spray. Providing the nozzles with additional outlets for spraying in opposite directions solves the problem of increasing the capacity of the de-aerator to a maximum degree and operating the double outlet nozzles at opposite sides of the central impingement plate between the same and the curved impingement plates results in a maximum de-aeration of the stock.

The central vertical impingement plate and the curved side impingement plates are of such width that the spray pattern of the nozzles will impinge against these plates and not mis the same and hit some of the areas of the vacuum tank beyond the impingement plates. The spray pattern is a function of the outlet diameter as well as the length of the nozzle. For the purposes of the present invention the nozzles should come as close as possible to a steady stream while projecting an atomized spray of stock in order to obtain a maximum flow rate and also the advantage of the bursting of the spray droplets when they impinge against the impingement plates. The curved side impingement plates 24 are arcuate and being located in the upper region of the vacuum tank extend upwardly and inwardly and converge toward the center of vertical impingement plate 23 and terminate at their bottom edge n open troughs or ledges formed by the reinforcmg flanges 58. Somewhat similarly the center plate 23 has at its lower edge a reinforcing bar 43 projecting laterally from its opposite side faces, and the central impingement plate assists in lreinforcing and strengthening the vacuum The double orifice supply nozzles are arranged in two rows extending longitudinally of the vacuum tank and located at opposite sides of the central impingement plate 23 and between the same and the side impingement plates 24. The flow of the stock through the branch conduits 2| from the headers |8 may be individually controlled by control valves 54, which are arranged exteriorly of the vacuum tank, as clearly shown in Fig. 1 of the drawings. These valves maintain the desired liquid level within the vacuum tank.

The outlet necks of each nozzle unit face in opposite directions and provide substantially a back-to-back arrangement of nozzles, one outlet neck facing the central impingement plate and the other facing one of the side impingement plates, with the central impingement plate arranged between and separating the two rows of nozzle units, as clearly illustrated in Fig. 4 of the drawings.

The central, vertical. impingement plate 23 which is located in the upper section of the vacuum tank extends longitudinally thereof substantially the entire length of the same. It is preferably supported at its lower edge upon a reinforcing horizontal bar 43 welded or otherwise secured to the central impingement plate and projecting from opposite faces thereof. The central impingement plate is also supported at its ends by vertical bars or strips 44 welded or other-. wise secured to the central impingement plate and also to the drum or shell of the vacuum tank, but any other suitable means may be provided for mounting the central impingement plate Which is supported at suitable intervals by vertical rods 45 connected at their upper ends to horizontal rods 45 which extend across the vacuum tank and pass beneath the horizontal bar 43. The horizontal rods reinforce the vacuum tank and maintain the cylindrical form of the shell of the vacuum tank and also dampen any vibrations that might be set up in the central impingement plate, as, for instance, should the nozzles be spraying at one side only of the central impingement plate. The central impingement plate on the larger jobs is a long plate and might get into a dangerous condition of vibration if it were not reinforced and braced by the horizontal rods 46. The vertical rods 45 are preferably two in number and are located on each side of the outlet 25 in the bottom of the vac-uum tank. This outlet is generally of a size which, unless covered by a grating or grid 41, might permit a man to drop accidentally through the outlet. It is also desirable to reinforce the shell of the vacuum tank at this point as there is a tendency during fabrication to warp at the bottom outlet. The

grating or grid 4'! consists of spaced parallel bars which extend across the outlet, and are welded or otherwise secured at their ends to the outlet. The grating is primarily installed to prevent any one working in the vacuum tank from slipping on the smooth lithcoted interior of the vacuum tank and from dropping down into the suction piping. If a man slipped and fell down the piping, it would be difficult to get him out in time to avoid serious injury. The grating performs further the function of cutting down to some degree the vortex action that occurs when liquid flows from a vessel into a piping. By cutting down this vortex action a more uniform flow of the liquid and a greater accuracy in controlling the same are obtained.

The side impingement plates 24 are arranged at opposite sides of the vacuum tank at the upper section thereof and are of sufficient area to receive the stock discharged from the nozzle outlet necks facing the outer sides of the two rows of nozzle units. The curved impingement plates may each be provided at its lower edge with an angular extension 58. The spray rushing down the sides of the tank would, unless diverted, carry with it some of the air and drive such air into the pool or body of liquid in the bottom of the tank. The angle bars or flanges 58 each preferably consist of a bar or flange welded to the curved impingement plate. By diverting the spray and throwing it upwardly and inwardly, such diverted spray is further disrupted by subjecting it to further vacuum action in removing air from the liquid. The curved impingement plates reinforce the sides of the vacuum tank.

The vacuum conduit 29 is provided with a plurality of branch conduits 48 .which are provided with outlets 49 having flange connections with the branches 4B and extending through the top of the Vacuum tank and projecting inwardly therefrom. The vacuum outlets 49, which may be of any desired number and which may be positioned at any desired points along the vacuum tank, by projecting downwardly into the vacuum tank several inches, perform a function and serve the purpose very similar to the purpose of the longitudinal angle bars '58 at the lower edges of the curved side impingement plates 24 and the central impingement plate 23. The spray hitting the interior of the vacuum tank splashes upwardly and downwardly and that portion of the stock which is sprayed against the top of the vacuum tank may contain air and be carried up through the vacuum lines. The extension of the outlet into the vacuum tank serves as a baffle plate or dam that deters stock particles in suspension in the atmosphere of the tank from being sucked into the conduit and reduces the possibility of stock being carried outwardly through the vacuum system.

The nozzles 22 project the stock to the interior of the vacuum tank in a swirling spinning cone of atomized spray of mist-like particles or droplets, so the sprayis spinnin as it hits the impingement plates or surfaces and is deflected in a direction that is tangential to the circle created by the interception of the hollow cone shaped spray with the impingement surface. In other words, the spray splashes in practically all directions in a plane normal to the axis of the spray core. The spray does not bounce off the surface at the same angle as it hits, as for instance does a ray of light. The atomized sprays of stock that are forcibly projected into the tank may intercept or cut off the air and water-vapor stream that is passing out of the tank through the vacuum outlet and thus creating a considerable pressure loss due to friction. This in turn has the effect of lowering the vacuum in the tank to a degree below the critical that is required for eflicient de-aeration. Therefore, with a View to overcoming this, the flanges 58 on the curved impingement plates and the bars 43 on the central vertical impingement plate seem to cause some of the stock flowing downwardly thereto or impinging thereon to be deflected or to rebound upwardly bringing about some increase in diffusion of the atomized stock particles, which not only gives the rebounding particles a further chance at de-aeration but makes for less resistant passage of the air and water-vapor to the vacuum outlet. These ledge-like surfaces are so scoured by the blast of the sprays that there is no tendency of stock to cling thereto.

The curved impingement plates are welded at their marginal edges 50 to the inner faces of the walls of the vacuum tank at the upper portion thereof and the rear faces of the impingement plates and also the contiguous surfaces of the vacuum tank are sealed by said marginal welding and in order to prevent moist air from being confined between the inner face of the curved impingement plate and the wall of the vacuum tank, the tank is provided with one or more weep holes 51 for each curved impingement plate. Weep holes of three-eighths of an inch diameter are sufficient for this purpose and a plurality of weep holes is preferably provided. After the curved impingement plates have been welded to the tank the interior of the tank and the surfaces of the impingement plates are coated with a protective baked-on synthetic resin for preventing corrosion of the metal of the plates. It has been found that unless such weep holes be provided, moist air contained between the curved impingement plates and-' the walls of the vacuum tank will be converted into steam during the baking of" the coating and damage the tank and the impingement plates. By providing the weep holes the moisture escapes during the baking of the coating.

After the coating has been applied to the interior of the tank and the surfaces of the impingement plates, the weep holes are closed by plugs 52 which are welded within the weep holes in spaced relation with the curved impingement plates, the intervening space 53 between the plug 52 and the impingement plate 24 preventingthe welding heat from injuriously' affecting the coating of the impingement plates. The plug 52 which is welded within the weep hole, may be tapered, as shown, and during the weldingprocess the plug 52 may be supported in the said spaced relation by the welding'flux employed or by any other suitable means.

' A conduit 55 provided with a control valve 56 leads from the pump 25 to the head box 51 of a paper making machine.

What we claim is:

1. Apparatus for treating flowable cellulosic stock to effect de-aeration thereof, which comprises a generally horizontal closed vacuum tank, means for applying vacuum-inducing suction therein through the upper portion of the tank, means for maintaining a pool of ole-aerated stock in the lower portion of the tank, means for removing de-aerated stock from that pool, a plurality of spray-nozzles in the upper portion of the tank, and from which stock is atoinizingly projected, imperforate impingement means for receiving spray so projected spaced from opposite sides of said nozzles, and a stock supply header for forcibly supplying stock to the spray-nozzles, said nozzles being in pairs with the nozzles of each pair located back to back and having oppositely facing outlets directed towards the impingement means, and there being a common stock-supply for each pair of nozzles.

2. Apparatus according to claim 1, wherein for each pair of oppositely directed nozzles there is a vertical impingement surface for one nozzle and a curved impingement surface for the other.

3. Apparatus according to claim 1, wherein'for one of each pair of nozzles there is a concavely curved impingement surface, and on the lower margin of that plate is an inwardlyextending open-ended trough for deflecting outwardly away therefrom stock sprayed onto the plate that runs down the plate to collect in the trough and to be conducted by it back to the pool in the tank bottom.

4. Apparatus according to claim 1, wherein the means for applying the vacuum-inducing suction includes a conduit, and the terminal of that conduit within the tank extends below the pe riphery of the tank to form a dam that deters stock particles in suspension in the atmosphere of the tank from being sucked into that conduit.

5. Apparatus for treating flowable'cellulosic stock to effect de-aeration thereof, which comprises a closed vacuum tank, means for applying vacuum-inducing suction therein, said tank being provided with impingement surfaces spaced from each other transversely of the tank, a double orifice nozzle located within the vacuum tank between said impingement surfaces and having outlets at opposite sides presented towards confronting impingement surfaces and adapted to spray the stock simultaneously against the impingement surfaces, means upon the impingement surfaces for intercepting downwardly moving sprayed stock and splashing the same upwardly to further de-aerate the splashed stock, a stock supply header for forcibly supplying stock to the spray nozzle and means for removing deaerated stock from the tank.

6. Apparatus for treating fiowable cellulosic stock to effect de-aeration thereof, which comprises a closed vacuum tank, means for applying vacuum-inducing suction therein, said tank being provided with spaced'impingeinent surfaces, one of the impingement surfaces being inclined upwardly and inwardly toward the other, a double orifice nozzle located within the vacuum tank between said impingement surfaces and having outlets arranged to'spray the stock simultaneously against the impingement surfaces, a'stock supply header for forcibly supplying stock to the spray nozzle and means for removing de-aerated stock from the tank.

'7. Apparatus for treating fiowable cellulosic stock to effect de-aeration thereof, which comprises a closed vacuum tank, means for applying vacuum-inducing suction therein, said tank being provided with spaced impingement surfaces, one of the impingement surfaces being vertical and the other curved and extending upwardly and inwardly toward the vertical impingement surface, a double orifice nozzle located within the vacuum tank between said impingement surfaces and having outlets arranged to spray the stock simultaneously against the impingement surfaces, a stock supply header for forcibly supplying stock to the spray nozzle and means for removing de-aerated stock from the tank.

8. Apparatus for treating flowable cellulosic stock to effect de-aeration thereof, which comprises a closed vacuum tank, means for applying vacuum-inducing suction therein, said tank being provided with spaced impingement surfaces, one of the impingement surfaces being vertical and the other curved and extending upwardly and inwardly toward the vertical impingement surface, and an open trough at the bottom of the curved impingement surface arranged to intercept downwardly rushing spray and cause the same to splash upwardly away from said curved impingement surface for further ale-aerating the splashed spray, a double orifice nozzle located within the vacuum tank between said impingement surfaces and having outlets arranged to spray the'stock simultaneously against the impingement surfaces, a stock supply header for forcibly supplying stock to the spray nozzle and means for removing de-aerated stock from the tank.

9. Apparatus for treating flowable cellulosic stock to effect de-aeration thereof, which comprises a closed vacuum tank, means for applying vacuum-inducing suction therein, said tank being provided with spaced impingement surfaces, one of the impingement surfaces being vertical and the other curved and extending upwardly and inwardly toward the vertical impingement surface, and an angle flange located at the bottom of the vertical impingement surface and arranged to intercept downwardly moving spray and cause the same to splash upwardly and away from the vertical impingement surface for further de-aeration of the splashed spray, a double orifice nozzle located within the vacuum tank between said impingement surfaces and having outlets arranged to spray the stock simultaneously against the impingement surfaces, 2, stock supply header for forcibly supplying-stock to the spray nozzle and 9 means for removing ole-aerated stock from the tank.

10. An apparatus for treating flowable cellulosic stock to effect de-aeration thereof, which comprises a closed vacuum tank, means for applying vacuum-inducing suction therein, said tank being provided at its upper portion at its sides with curved impingement surfaces extending upwardly and inwardly, a vertical impingement plate located in the tank between said curved impingement surfaces double orifice nozzles located between the vertical impingement plate and the curved impingement surfaces and having outlets arranged to spray in opposite directions upon said impingement plate and said curved impingement surfaces, a stock supply header for forcibly supplying stock to the spray nozzles and means for removing de-aerated stock from the tank.

11. An apparatus for treating flowable cellulosic stock to efiect de-aeration thereof, which comprises a closed vacuum tank, means for applying vacuum-inducing suction therein, said tank being provided at its upper portion at its sides with curved impingement surfaces extending upwardly and inwardly, a vertical impingement plate located in the tank between said curved impingement surfaces, double orifice nozzles located between the vertical impingement plate and the curved impingement surfaces and having outlets arranged to spray in opposite directions upon said impingement plate and said curved impingement surfaces, open troughs located at the bottoms of the curved impingement surfaces for intercepting spray and causing the same to splash upwardly, a bar secured to the lower edge of the vertical impingement plate and projecting from opposite sides thereof and arranged to cause spray moving downwardly at both of the faces of the vertical i. 9 plate to splash upwardly and outwardly from the plate, a stock supply header for forcibly supplying stock to the spray nozzles and means for removing de-aerated stock from the tank.

12. An apparatus for treating fiowable cellulosic stock to efiect a ole-aeration thereof, including a tank provided with a weep hole, an imperforate impingement plate arranged against the interior surface of the tank over the weep hole and marginally welded to the tank and sealed throughout its marginal edges to the tank wall, a baked coating covering the impingement plate and adjacent surfaces of the tank, and closure means for the weep hole consisting of a plug welded within the weep hole in spaced relation with the impingement plate to insulate the impingeemnt plate and prevent the welding from injuring the coating.

CARLETON L. CLARK. CARLO VICARIO. CORNELIUS J. LYON S. JANIE'S A. SMITH. WM. W. HICKEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 280,905 Brownell July 10, 1883 474,490 Walter May 10, 1892 1,396,632 Jensen Nov. 8, 1921 1,883,662 Fisher Oct. 18, 1932 1,910,088 Cherry May 23, 1933 2,201,870 Piercy et al May 21, 1940 2,247,897 Wahlin July 1, 1941 2,346,423 Gray Apr. 11, 1944 2,484,577 Murphy Oct. 11, 1949 2,614,656 Clark et al. Oct. 21, 1952

Images