Abstract:
The invention creates a device for deaerating fiber stock suspension including a horizontal cylinder tank, an inlet, an outlet opening, and a vacuum connection. An overflow tube may be positioned independently of the location of the inlet for the fiber stock suspension and the outlet for the deaerated fiber stock suspension.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the invention.  
           [0002]    The present invention relates to a device for deaerating a fiber stock suspension.  
           [0003]    2. Description of the related art.  
           [0004]    Devices for the deaeration of fiber stock suspensions are well known to the experts in the industry. As the name indicates, these devices deaerate fiber stock suspensions. During deaeration minor contaminates which would otherwise interfere with paper or cardboard production are removed. The devices are large tanks into which the fiber stock suspension, that is to be supplied to the paper or cardboard machine, is fed in the form of a thin mixture. The functional principle of the device is that the fiber stock suspension is boiled in a vacuum, the gas is removed to a so-called gas chamber, and the other minor impurities present on the liquid surface in the tank are discharged. The fiber stock suspension which is to be supplied to the paper or cardboard machine is removed through an opening in the tank floor, located there for the purpose of removing fiber stock suspension from the tank that is as gas free as possible. In order to maximize the deaerating capabilities of the device, a vacuum is generated in the tank by a pump, whereby the gas is forced through a line from the tank. The deaerating capability is improved when the supplied gas-containing fiber stock suspension is fed into the tank through steel pipes located above the liquid level in the tank whereby the gas which is present in the added fiber stock suspension, possibly in the form of bubbles is discharged prior to coming into contact with the already present fiber stock suspension. In addition to stabilizing the liquid level, the single overflow is used to remove minor contaminations from the liquid surface in the tank, so they do not reach the paper or cardboard machine. The minor contaminates flow over the single overflow to the discharge and then on to further treatment.  
           [0005]    German Disclosure Document DE 42 34 522 A1 describes a deaeration chamber in accordance with the aforementioned generic term of the present invention, as used in the paper and pulp industry. The separation wall which forms the overflow for the separated, excess fiber stock suspension is essentially level with the rear edge of the outlet for the gas-free suspension and the overflow for the separated, excess suspension itself slopes toward the overflow in the tank, in opposite direction to the flow direction.  
           [0006]    Further disclosures regarding the position and shape of the separation wall forming the overflow for the separated, excess fiber stock suspension may be found in the German prior art documents DE 32 19 740 A1, in the PCT application WO 97/15717 and in U.S. Pat. No. 5,868,905 (PK10542 US).  
           [0007]    All aforementioned documents share the disadvantages with regard to the overflow for the separated, excess fiber stock suspension in that the separation wall is located transversely and symmetrically to the tank axis (longitudinal axis), that it&#39;s location is a given due to it&#39;s shape, meaning that it is located on one of the two end areas of the tank and it&#39;s overflow length is fixed.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides a device for deaerating of fiber stock suspension where the overflow for the separated, excess fiber stock suspension can be located independently from both the inlet for the fiber stock suspension and the outlet for the deaerated fiber stock suspension. An overflow in the shape of an overflow pipe having an overflow height and an overflow length located prior to the outlet opening for the separated, excess fiber stock suspension, viewed in the flow direction.  
           [0009]    In one embodiment of the invention a dwell chamber in the form of a hydraulic stabilizer is located after the outlet opening for the gas-free fiber stock suspension. The dwell chamber consisting of preferably a long horizontally cylindrical tank, with at least one inlet opening to accept the fiber stock suspension coming from a prior tank. The tank having outlet openings for the separate discharge of the gas-free fiber stock suspension, the separated gas, the excess fiber stock suspension and the separated, excess fiber stock suspension. The opening for the discharge of the separated excess fiber stock suspension being an overflow tube having an overflow height and an overflow length.  
           [0010]    By designing the overflow for the separated, excess fiber stock suspension as an overflow tube having an overflow height and an overflow length, a design advantage as well as a fluidic advantage is achieved in that the overflow for the separated, excess fiber stock suspension may be positioned at any desired location in the tank; rather than being positioned transversely and symmetrically to the tank axis in one of the two end areas of the tank. Further, the design of the overflow length may be freely selected within a certain range.  
           [0011]    In one embodiment of the invention the overflow pipe has a funnel shaped opening with an aperture angle of between 30° and 80°, preferably between 40° and 50°. This type of initial opening has an advantage in that the opening orifice area of the overflow tube is independent from the continuing diameter of the overflow tube. In addition, the flow geometry can be positively influenced by the selection of the aperture angle.  
           [0012]    One embodiment of the invention provides that the overflow tube be a telescopic structure, thereby offering a changeable overflow height. Changeability of the overflow height provides the option to control the liquid level in the tank, or to regulate it, if a drive unit including a control system are present, whereby the liquid level will influence the dwell duration and the dwell volume of the fiber stock suspension in the tank. The telescopic construction of the overflow tube may be a sliding device.  
           [0013]    A further embodiment of the invention provides, that the overflow tube including the discharge pipe be movable, thereby providing for an adjustable overflow height. The discharge pipe of the overflow tube also may have a transition piece whose length and shape are adjustable so that, even if the overflow tube is moved, no local shifting occurs in the subsequent system. The transitional piece would preferably be in the form of folded tubing.  
           [0014]    In yet a further embodiment of the invention the overflow tube is a telescopic and divergent structure, providing for an adjustable overflow length. An increased overflow length provides the advantage of additional abatement due to reduced flow in the separated, excess fiber stock suspension.  
           [0015]    In a preferred embodiment of the invention, the overflow tube can be coupled with at least one tube segment, thereby providing adjustability for the overflow height and/or the overflow length. Depending upon the shape of the pipe segment, the configuration may influence the overflow height and/or overflow length without having to fall back upon expensive and operationally critical mechanisms.  
           [0016]    In a further embodiment of the current invention the outlet opening for the separated, excess fiber stock suspension is located between the inlet opening for the fiber stock suspension and the outlet opening for the gas-free fiber stock suspension. Thereby the contaminated fiber stock suspension can be brought directly, without having to pass the outlet for deaerated fiber stock suspension, to the outlet opening and be removed.  
           [0017]    In another embodiment of the invention the tank includes at least two outlet openings for separated, excess fiber stock suspension, whereby at least one outlet opening is designed as an outlet in the form of an outlet pipe with an overflow height and an overflow length and the additional outlet openings are equipped with covers. The presence of multiple outlet openings offers the technological advantage that the overflow which is designed as an overflow pipe may be located at various positions in the tank and therefore, it&#39;s specific location can be selected to best suit the fiber stock suspension characteristics.  
           [0018]    In a further embodiment of the invention an overflow, designed as an overflow pipe with an overflow height and an overflow length is located prior to the outlet opening for the gas-free fiber stock suspension, as viewed in the direction of flow. The advantage is that the overflow for the gas-free fiber stock suspension can be placed at any desired location in the tank. It further provides the advantage that different volumes can be discharged in a fluidically optimum manner, by means of different size openings.  
           [0019]    In a further embodiment of the invention a device is provided for producing vacuum in the tank including a vacuum connection, a vacuum line and at least one vacuum pump. Several vacuum connections can, at any given time, be operated individually with a separate vacuum line and a separate vacuum pump, or with individual vacuum lines and a common vacuum pump.  
           [0020]    A further embodiment of the invention provides that in the upper interior tank area several nozzles are located for moistening the interior surface of the tank which does not come into contact with the fiber stock suspension, whereby the speed and efficiency of the fiber stock deaeration process taking place in the tank is positively influenced. Moisturizing also prevents fiber stock or ash deposits.  
           [0021]    It is also advantageous if the distributer pipe is parallel or approximately parallel to the tank axis. The distributer pipe can be outside or inside the tank. This arrangement results in spacial (space requirement) and technological (distribution uniformity) advantages.  
           [0022]    In a further embodiment of the invention the hydraulic stabilizer for the preferably gas-free fiber stock suspension is a dwell tank having a certain dwell duration and a certain dwell volume having fluidically optimum interior contours. The fluidically optimum interior contour is that of a horizontal cylinder, or that of a conical tube, aligned in the direction of flow of the fiber stock suspension. This hydraulic stabilizer is particularly suitable for new line installations for deaerating of fiber stock suspensions whose design principles for the tank construction in each case is disclosed in the aforementioned U.S. Pat. No. 5,868,905 (PK10542 US).  
           [0023]    A further embodiment of the invention provides that, the dwell duration of the preferably gas-free fiber stock suspension in the hydraulic stabilizer is between 2 and 80 seconds, preferably between 5 and 40 seconds; and the dwell volume of the preferably gas-free fiber stock suspension in the hydraulic stabilizer is between 0.8 and 100 m 3 , preferably between 4 and 70 m 3 . These parameters have the advantage that they ensure optimum design of the above constant section and optimum operation as far as runability, etc. of the paper or cardboard machine. The hydraulic stabilizer is located immediately or indirectly following the outlet opening for the preferably gas-free fiber stock suspension.  
           [0024]    According to the preferred embodiment of the invention there is located between the outlet opening for the preferably gas-free fiber stock suspension and the hydraulic stabilizer, at least one tube or pipeline.  
           [0025]    It is also understood that the aforementioned and subsequently further explained characteristics of the invention may be utilized not only in the cited combinations, but also in other combinations, or self-contained, without relinquishing the scope of the invention.  
           [0026]    Additional characteristics and advantages of the invention result from the subclaims and the following description of preferred design examples, whereby reference is made to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0028]    [0028]FIG. 1 is a schematic and sectional side view of a device for deaerating a fiber stock suspension embodying the present invention;  
         [0029]    [0029]FIG. 2 is another schematic and sectional side view of a device for deaerating a fiber stock suspension also embodying the present invention;  
         [0030]    [0030]FIG. 3 is yet another schematic and sectional side view of a device for deaerating a fiber stock suspension also embodying the present invention; and  
         [0031]    [0031]FIG. 4 is yet still another schematic and sectional side view of a device for deaerating a fiber stock suspension also embodying the present invention. 
     
    
       [0032]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0033]    Referring now to the drawings, and more particularly to FIG. 1, there is shown device  1  for deaerating fiber stock suspension  2  including horizontal tank  3  with a tank axis  3   a  into which fiber stock suspension  2 , is supplied to a paper or cardboard machine, and is fed in the form of a thin mixture through at least one distributer pipe  4  which is parallel to tank axis  3   a  and from which a plurality of successive jet tubes  5  originate for feeding fiber stock suspension  2  into tank  3 . The flow direction of fiber stock suspension  2  is shown by directional arrows ‘S’. In an effort to improve the deaerating capabilities of device  1  introduced fiber stock suspension  2  which, at this point still contains gas, is fed through jet tubes  5  above liquid level  6  in tank  3 , whereby gas  7  which may be present in the form of bubbles in fiber stock suspension  3  is separated before introduced fiber stock suspension  2  comes into contact with fiber stock suspension  2  already present in tank  3 . Jet tubes  5  terminate in slightly below tank ceiling  8 , reinforcing the deaeration process of fiber stock suspension  2 , since fiber stock suspension  2  impacts with tank ceiling  8 .  
         [0034]    Referring additionally now to FIG. 2, a supply of fiber stock suspension  2  can also occur through a chamber system. Further, the addition of fiber stock suspension  2  may also occur in at least one of the ways described in unpublished German patent application DE 199 47 905.4 (PK10987 DE); its contents is herewith made the object of this description. In the upper area of tank ceiling  8  vacuum connection  9  with vacuum line  10  is connected to vacuum pump  11 . Vacuum connection  9  may alternatively be located in a side area of tank ceiling  8 . By connecting tank  3  to vacuum pump  11  the deaerating capability of device  1  is maximized, whereby gas  7  is pumped from tank  3  by vacuum pump  11 .  
         [0035]    Further, in the area of tank ceiling  8  facing away from jet tubes  7 , several nozzles  13  are provided for the purpose of moistening tank surface  14  which is not in contact with fiber stock suspension  2 . This positively influences the speed and efficiency of the fiber stock suspension deaeration process taking place in tank  3 . Outlet opening  15  which flows into pipe system  16  for the purpose of discharging gas-free fiber stock suspension  2 . 1  is provided in the area of tank  3  which is facing away from distributor pipe  4 . Between distributor pipe  4  and outlet opening  5  for gas-free fiber stock suspension  2 . 1 , outlet opening  17  is provided for the separated, excess fiber stock suspension  2 . 2  which runs into pipe system  18  for the purpose of returning excess fiber stock suspension  2 . 2  into the circulation loop which is not illustrated here, which however, is well known in the art.  
         [0036]    In one embodiment of the invention device  1  includes overflow  20  with overflow tube  19  having an overflow height H Ü  and an overflow length L Ü  located prior to outlet opening  17  to accommodate the flow of the separated, excess fiber stock suspension. Overflow tube  19  may be cylindrical or it may have a funnel like initial opening  21  having an aperture angle α, as illustrated in FIG. 1. The overflow length L Ü  is calculated from the initial circumference of initial opening  21 . The aperture angle α generally assumes a value of between 30° and 80°, preferably between 40° and 50°. Overflow pipe  19  including discharge pipe  18  may be designed movably in accordance with the sliding mechanism indicated by double arrow  22 ; allowing for adjustment in overflow height H Ü . Weir  38  attached to the interior of tank  3  is located to deflect flow of the fiber stock suspension. In a preferred embodiment, pipe system  18  is adjustable in its length and form, such as a folded tube or similar. Overflow pipe  19  may be telescopic and divergent in nature providing adjustability of overflow height H Ü . Overflow pipe  19  may be coupled with at least one pipe segment which will alter overflow height H Ü  and/or overflow length L Ü . Tank  3  may also include at least two outlet openings  17 , for separated excess fiber stock suspension  2 . 2 . At least one outlet opening  17  is designed as outlet  20  in the form of an outlet pipe  19  with an overflow height H Ü  and an overflow length L Ü  and whereby the at least one additional outlet opening is equipped with cover  36 .  
         [0037]    A schematic sectional side view of a second preferred embodiment of device  1  for deaerating fiber stock suspension  2 , is illustrated in FIG. 2. Tank  3  inclusive of component parts and component groups of device  1  is described in the US-patent documentation U.S. Pat. No. 3,538,680 (≈DE-A 17 61 496). The content of this aforementioned patent document is herewith made the object of this description. The supply of fiber stock suspension  2  into tank  3  occurs via a plurality of communicating chambers  23 , whereby only two chambers  23  are indicated schematically. Communicating chambers  23  are located above liquid level  6  of fiber stock suspension  2  in tank  3 . Please refer to FIGS. 1 and 2 regarding possible arrangement of outlet opening  17 , including overflow pipe  19  for separated, excess fiber stock suspension  2 . 2 . Overflow  25  in the form of overflow pipe  24  having overflow height H Ü1  and overflow length L Ü1  is located prior to outlet opening  15  for directing the flow of the gas free fiber stock suspension  2 . 1 .  
         [0038]    Concerning the arrangement of overflow pipe  24  we refer you to the details in FIG. 1 pertaining to overflow pipe  19  and overflow  20  for the flow of separated, excess fiber stock suspension  2 . 2 .  
         [0039]    Additionally referring to FIG. 3 there is shown device  1  designed for deaerating of fiber stock suspension  2 . Device  1  includes horizontal cylindrical tank  3  with a tank axis  3   a  into which fiber stock suspension  2 , that is to be supplied to the paper or cardboard machine, is fed in the form of a thin mixture through at least one distributer pipe  4  from which a multitude of successive jet tubes  5  originate for feeding fiber stock suspension  2  into tank  3 . Regarding additional design characteristics please refer to tank  3  illustrated in FIG. 1. Outlet opening  26  for the flow of gas free fiber stock suspension  2 . 1  is located in floor  27  of tank  3 . A vacuum in tank  3  is provided by way of vacuum connection  9 , vacuum line  10 , at least one vacuum pump  11 , optional condensers  37  and continuing line  12  near tank ceiling  8 . Further, in the area of tank ceiling  8  facing away from jet tubes  5 , nozzles  13  are provided for the purpose of moistening interior tank surface  14  which is not in contact with fiber stock suspension  2 .  
         [0040]    Dwell chamber  28  in the form of hydraulic stabilizer  28 . 1  is located after at least one outlet opening  26  for the preferably gas-free fiber stock suspension  2 , viewed in direction S. Dwell chamber  28  including preferably a long horizontally cylindrical tank, at least one inlet opening  29  to accept fiber stock suspension  2  coming from tank  3 , at least one each outlet opening  30 ,  31 ,  32  located in tank  28 . Outlet opening  30  provided for the flow of gas-free fiber stock suspension  2 . 1 . Outlet opening  31  provided for the flow of gas  9 , outlet  32  being provided for the flow of excess fiber stock suspension  2 . 2 . Weir  38  may be attached to the interior of tank  3  and dwell chamber  28  being located to deflect flow of the fiber stock suspension. Overflow  33  in the embodiment of overflow tube  34  having overflow height H Ü  and overflow length L Ü . Regarding the arrangement of overflow tube  34  we refer you to the details in FIG. 1 of overflow pipe  19  of overflow  20  for separated, excess fiber stock suspension  2 . 2 .  
         [0041]    Hydraulic stabilizer  28 . 1  for preferably gas free fiber stock suspension  2  offers a dwell volume V V  of between 0.8 and 100 m 3 , preferably between 4 and 70 m 3 , and dwell duration V D  of preferably gas-free fiber stock suspension  2  in hydraulic stabilizer  28 . 1  is between 2 and 80 seconds, preferably between 5 and 40 seconds. Hydraulic stabilizer  28 . 1  is connected indirectly by tubing or piping with outlet opening  26  for the passage of preferably gas-free fiber stock suspension  2  and is located downstream from it.  
         [0042]    Now further referring to FIG. 4 there is shown device  1  for deaerating fiber stock suspension  2 , similar to FIG. 3. Tank  3  is consistent with tank  3  shown in FIG. 2 in a different view; we therefore refer you to FIG. 2 for the further description. Tank  28  is consistent with tank  28  illustrated in FIG. 3; therefore we refer you to FIG. 3 for further details.  
         [0043]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.  
       Component identification index  
       [0044]    [0044] 1  Device (for deaerating fiber stock suspension)  
         [0045]    [0045] 2  Fiber stock suspension  
         [0046]    [0046] 2 . 1  Gas free fiber stock suspension  
         [0047]    [0047] 2 . 2  Separated, excessive fiber stock suspension  
         [0048]    [0048] 3  Tank  
         [0049]    [0049] 3   a  Tank axis  
         [0050]    [0050] 4  Distributer pipe  
         [0051]    [0051] 5  Jet tube  
         [0052]    [0052] 6  Liquid level  
         [0053]    [0053] 7  Gas  
         [0054]    [0054] 8  Tank ceiling  
         [0055]    [0055] 9  Vacuum connection  
         [0056]    [0056] 10  Vacuum line  
         [0057]    [0057] 11  Vacuum pump  
         [0058]    [0058] 12  Line  
         [0059]    [0059] 13  Nozzle  
         [0060]    [0060] 14  Tank interior surface  
         [0061]    [0061] 15 , 17 , 17 . 1   
         [0062]    [0062] 26 , 30 , 31 , 32  Outlet opening  
         [0063]    [0063] 16 , 18  Piping system (discharge)  
         [0064]    [0064] 19 , 24 , 34  Overflow pipe  
         [0065]    [0065] 20 , 25 , 33  Overflow  
         [0066]    [0066] 36  Cover  
         [0067]    [0067] 21  Funnel shaped initial section  
         [0068]    [0068] 22  Direction of movement  
         [0069]    [0069] 23  Chamber  
         [0070]    [0070] 27  Tank floor  
         [0071]    [0071] 28  Tank  
         [0072]    [0072] 28 . 1  Hydraulic Stabilizer  
         [0073]    [0073] 29  Inlet opening  
         [0074]    [0074] 37  Condenser  
         [0075]    [0075] 38  Weir  
         [0076]    H Ü , H Ü1  Overflow height L Ü , L Ü1  Overflow length S Direction of flow (arrow) α Aperture angle