Abstract:
A packing material unit for liquid-gas contact apparatus which has a first plurality and a second plurality of loops ( 15 ) being at a first angle (loop  15 ) or a second angle (loops  15′  and  15″ ), respectively, the second angle being the opposite of the first angle, with the first loops and the second loops alternating, and an interior support for maintaining the loops of at their respective angles. The loops have an interior point and an exterior point, and an interior support connects the interior points. There is also an exterior ring ( 25 ) for connecting the exterior points of the loops. The loops, interior support, and exterior ring also have a plurality of protuberances ( 35, 65, 95 ).

Description:
The present invention is related to Provisional Application Ser. No. 60/099,326, filed on Sep. 6, 1998. 
    
    
     TECHNICAL FIELD 
     The present invention relates to packing units used in air pollution control equipment, gas and liquid contact apparatus for absorption or desorption of gas, rectification columns, mist and entrainment separation of solid and liquid particulates, and the like. 
     BACKGROUND OF THE INVENTION 
     Packing materials are of various sizes and shapes, usually designed to bring two phases of a system, typically a gas or mist and a liquid, into intimate contact. Filamentous packing materials are disclosed in U.S. Pat. Nos. 2,867,425 and 3,752,453. Other known packing configurations are Berl saddles and Raschig rings. 
     Packing materials accomplish their purpose either by presenting an extended thin film of one phase, usually the liquid, to the other phase or by constantly renewing the surface of one phase, usually the liquid, so that the most efficient mass transfer between phases can occur with the least expenditure of energy. The surface area of the packing material is therefore an important factor. 
     Interstitial holdup points are points where the surface of one phase is renewed by agglomeration and redispersion, to provide a fresh unsaturated surface to the other phase. The number of interstitial holdup points provided per cubic foot of packing material is thus extremely important. 
     Interstitial holdup points are provided both by the shape of the packing material unit and by its intersections with the packing material units (“packing units”) immediately surrounding it. Interlocking increases the number of contact points between packing units and therefore increases the number of interstitial holdup points. However, interlocking also has disadvantages, such as the tendency to block fluid flow and thus increase the pressure drop through the packed space, such as a packed column. Interlocking where a packing unit fits within another packing unit is referred to as “nesting” and can dramatically block the fluid flow and significantly increase the pressure drop. Extensive interlocking also requires more packing units per cubic foot, thereby increasing the weight and cost, which are particularly significant considerations in large installations. 
     Interlocking can be prevented, but this usually reduces the number of interstitial holdup points. Therefore, complete prevention of interlocking of prior art packing units may not be desirable. The preferred packing unit would provide a large number of independent interstitial holdup points so that reliance for such holdup points from contact with other packing units by interlocking is lessened, and interlocking can be reduced without significant adverse effect. Such a packing unit would have the capacity to provide better phase surface regeneration even without being interlocked with other packing units and would simultaneously require less pressure drop through the packed space, thus increasing efficiency. 
     SUMMARY OF THE INVENTION 
     Accordingly one object of the present invention to provide a packing unit for a liquid-gas contact apparatus by which more efficient operation of the apparatus is achieved while using fewer packing units per cubic foot. 
     Another object of this invention is to provide a packing material unit which provides for less interlocking with other packing units thereby requiring fewer units per cubic foot while simultaneously providing within each packing unit an increase in contact between the gas and liquid phases passing through the apparatus. 
     A further object of this invention is to provide more independent interstitial holdup points, and thus better phase surface regeneration, in an individual packing unit, thus reducing dependency on contact by the packing unit with surrounding or interlocked packing units to achieve the desired number of holdup points. 
     Still another object of the present invention is to provide a packing unit which results in the maximum time for mass transfer between the liquid phase and the gas or mist phase by increasing within the unit itself the number of points of surface regeneration. 
     Yet another object of this invention is a packing unit which provides a longer retention time of the liquid phase passing through a liquid-gas contact apparatus while reducing the pressure drop in the gas phase through the apparatus. 
     By the present invention, a surface or surfaces of a packing unit are provided with sharply contoured projections which define abrupt interruptions to liquid flow along the surface and which reduce interlocking between adjacent units. 
     Such projections can be of any number of different structural configurations designed to achieve rapid breaking up of liquid flow contacting the projection either as a result of impact therewith by dropping from a unit thereabove or by contact therewith during flow along the packing unit surface. For example, the projections can be cylindrical, square, rectangular, triangular, chisel pointed, oval shaped, or diamond shaped. It is necessary that the projections or recesses define abrupt changes in the surface contour to cause immediate splitting or breaking of liquid impinging thereagainst to facilitate rapid surface regeneration. Such splitting or breaking of liquid is distinguished from unit surface configurations designed simply to provide a larger surface area and then to spread or guide liquid flow evenly relative to or across that surface area. The present invention is characterized by providing more holdup points and at the same time more positive breaking of liquid flow whereby acceleration of surface regeneration is achieved without the degree of interlocking heretofore required to achieve the desired number of holdup points. 
     Although applicable to any of the known packing unit configurations, such as the Berl saddles and Raschig rings mentioned above, the present invention is described in conjunction with a filamentous packing unit. Such a filamentous packing unit may be provided in any suitable configuration and is described herein in a preferred form which is a torus having a plurality of loops having internal offsets, an exterior ring, and an interior support. The loops, the exterior ring, and the interior support each have protuberances which provide interstitial holdup points. It will be appreciated that the specific loop configuration described hereinafter is but one of many loop configurations which could be designed without departing from the basic configuration of a plurality of loops having internal offsets and being oriented about a central axis. 
     In the preferred packing unit configuration, each loop is a filament having a first half in a first plane and a second half in a second plane, the two planes preferably being parallel and slightly offset from each other, so that a loop is not in a single plane, and the two halves conveniently being joined to each other at their open ends. This loop configuration is altered by abrupt internal projections, external projections, and internal connecting projections. The internal connecting projections connect a point on a first half of the loop with a point on the second half of the loop so as to provide a pathway between those points and provide strength to the loop and to the packing unit. 
     Each loop is connected to first and second adjacent loops, with a first half of the loop being connected by one or more cross bridges to a corresponding first half of a first adjacent loop, and with the second half of the first loop being similarly connected by one or more cross bridges to a corresponding second half of a second adjacent loop. In addition, the cross bridges preferably have projections. 
     The first and second planes of a loop are mirror planes to the first and second planes of an adjacent loop. That is, the first planes are not parallel to each other and will intersect, and the second planes are not parallel to each other and will intersect. 
     The external ring has a plurality of first projections which extend radially outward from the ring, and a plurality of second projections which extend coaxially with the ring. The external ring preferably encircles and is connected to the outer open ends of the loop halves. 
     The interior support is connected to the inner open ends of the loops, has a plurality of interior projections which converge at the axis of the interior support, and has a plurality of exterior projections which extend coaxially with the axis of the interior support and the packing unit. 
     This configuration effectively reduces nesting or interlocking of packing units, and defines a plurality of holdup points therein. The abrupt changes in the surface contour of the loops and ring of the preferred embodiment advantageously lend to the manufacture of a packing unit which provides numerous small targets for the inertial impactment of liquid or solid particulates from an airstream. A multitude of small targets is well established as providing better efficiency in particulate removal. The preferred embodiment of this invention allows the interstitial or surface renewal points to be maintained for maximum gas absorption or desorption, while obtaining good efficiencies in particulate removal as well. By reducing interlocking and compacting of the units a reduction in pressure drop through a body of packing units is achieved as compared to prior art units which provide the same degree of removal. 
     This configuration provides substantial strength, such that the packing units can be stacked to large heights and handled with little care without collapsing or distorting. This benefit is provided with little added weight or cost over conventional packing units. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a side elevation view of the preferred embodiment of the packing unit. 
     FIG. 2 is a cutaway view along plane A-A′ of FIG.  1 . 
     FIG. 3 is a cutaway view along plane B-B′ of FIG.  1 . 
     FIG. 4 is a view of two loops along plane C-C′ of FIG.  2 . 
     FIG. 5 is a view of the cross bridges between two loop halves. 
     FIG. 6 is a side view of a loop. 
     FIG. 7 is a view of the intersection of the loop halves. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The packing units of the present invention are preferably produced from a material which is not affected by the process conditions. Accordingly, many plastic materials are suitable for use in making the packing units. Polypropylene, polyethylene, polyvinyl chloride, chlorinated polyvinyl chloride, nylon, fluorocarbons, polystyrene and the like are suitable materials. Preferably polyethylene is employed, and injection molding is used to manufacture the packing units. Although plastic materials are preferable, metals can be employed to produce packing units. The present invention provides the following advantages: fewer packing units of the present invention are required per cubic foot of packing space; the pressure drop achieved with the packing units of the present invention is less than for prior art packing units; the efficiency of a single packing unit of the present invention is similar to that of prior art units but at a lower pressure drop; and the packing units of the present invention are less prone to nesting. 
     Savings in the capital cost and the cost of operation of a packed separation unit can be readily achieved employing the packing units of the present invention. In this respect, fewer packing units per cubic foot are required and the gas fan horsepower can be less in view of the lower pressure drop through the unit, thus achieving a high level of efficiency. 
     The above benefits are derived by providing for the individual packing units to have sharply defined deviations from the surface contours thereof, which deviations function both to increase the number of holdup or drip-off points on the unit itself and reduce the amount of interlocking with an adjacent unit, and to have adjacent loops to be in different planes, which also function to reduce the amount of interlocking with an adjacent packing unit. Thus, in a given mass of such packing units, fluid flowing therethrough, influenced by gravity only and not by forced flow, impinges against an abrupt projection and is immediately broken or diverted to leave the surface of one packing unit and drop to another surface of the same packing unit or a surface of another packing unit. Thus, rapid surface regeneration is realized. Moreover, the reduction in interlocking provides a less compact mass and thus provides for less pressure drop of gas passing through the mass. The increase in holdup or drop-off points per unit together with the decrease in interlocking provides for separation apparatus operation with fewer packing units per cubic foot without adversely affecting efficiency. In addition, the design provides for increased structural strength so that the packing units are less susceptible to damage. 
     The packing unit of the present invention provides more turbulence than prior art packing units, provides more surface area, provides more renewal of the liquid surface area, provides a low pressure drop, is very resistant to nesting, is very lightweight, is very strong, is larger than prior art units so fewer packing units are required per unit of volume. Further, the packing unit may be used to remove gases from a liquid in addition to the standard use of remove particulates and solubles from a gas. 
     Refer now to the drawings in which like numerals represent like components throughout the several figures. FIG. 1 is a side elevation view of the preferred embodiment of the packing unit  10 . A packing unit  10  has a diameter of approximately 4 inches, and a height of approximately 2½ inches. FIG. 2 is a cutaway view along plane A-A′ of FIG. 1, and FIG. 3 is a cutaway view along plane B-B′ of FIG. 1. A packing unit  10  comprises a plurality of loops  15 , an exterior ring  25 , and an interior support member  30 . FIG. 4 is a view of two loops  15  along plane C-C′ of FIG. 2 with the exterior ring  25  being shown for reference. A loop  15 , not including protuberances, has a height of approximately 2 inches, and a width of approximately 1⅛ inches, and the filament forming the loop has a thickness of approximately 0.113 inches, and a width of approximately {fraction (1/16)} inch. 
     Referring to FIG. 4, for convenience of manufacturing, the top half  15 A of a loop  15  is identical to the bottom half  15 B of a loop  15 . Therefore, the view of the packing unit  10  along plane A-A′ in FIG. 2 is almost symmetrical to the view of the packing unit  10  along plane B-B′ in FIG.  3 . However, these views of the packing unit  10  are not exactly symmetrical because the view along plane B-B′ (the bottom half of the packing unit  10 ) is rotated slightly with respect to the view along plane A-A′ (the top half of the packing unit  10 ). Therefore, the plane of the top half  15 A of a loop will be parallel to, but slightly offset from, the plane of the bottom half  15 B of the loop. 
     The top half  15 A of a loop is connected to the bottom half  15 B of the loop by a rib  30 , which is in the form of an “X”. One leg of the “X” of the top half of the rib  30  is almost in the same plane as the top half  15 A of a loop, and the other leg of the “X” of the top half of the rib  30  is almost perpendicular to that plane. Similarly, one leg of the “X” of the bottom half of the rib  30  is almost in the same plane as the bottom half  15 B of a loop, and the other leg of the “X” of the bottom half of the rib  30  is almost perpendicular to that plane. The term “almost” is used because the planes of loop halves  15 A and  15 B are parallel, but offset, and the rib  30  must traverse the offset, so it is not exactly parallel to or perpendicular to either plane. A rib preferably has a thickness of ⅛ inch from one end of leg to the other end of a leg, with a leg preferably having a thickness of approximately {fraction (3/64)} inch. 
     A loop  15  has a plurality of exterior protuberances  35 , each of which protuberances  35  is approximately {fraction (3/32)} inch high and is preferably a {fraction (1/16)} inch square post with a flat end, and which is preferably in the same plane as the half of the loop  15  to which it is connected. A typical protuberance  35  has a short side and long side because it is mounted on a curved surface so the height above is the short side. 
     A loop  15  also has a plurality of interior protuberances  40 , each of which protuberances  40  is approximately ½ inch long and is preferably a T-post with a flat end, with the top of the “T” being in the same plane as the half of the loop  15  to which it is connected. As described below, a loop half is also connected to a corresponding loop half of an adjacent loop, and the leg of the “T” is pointed toward that adjacent loop half. 
     The loops  15  dispose generally radially outward from the central axis  45  of the packing unit  10  with one vector of the plane of a loop half, for example  15 A, proceeding radially outward, and being perpendicular to, the axis  45 , and with the other vector of the plane being slightly angled with respect to the axis  45 . Thus, the loops are slightly slanted, when the packing unit is viewed from the side, such as FIG.  1 . Furthermore, the slant of a loop  15  is opposite to the slant of adjacent loops, such that the plane of the top half  15 A of a loop  15  and the plane of the top half  15 A′ of an adjacent loop  15 ′ would meet. Likewise, the plane of the bottom half  15 B of a loop  15  and the plane of the bottom half  15 B″ of an adjacent loop  15 ″ would meet. 
     FIG. 5 is a view of the cross bridges between two loop halves. In the preferred embodiment, as shown by FIGS. 1 and 5, the top half  15 A of a loop and the top half  15 A′ of an adjacent loop  15 ′ are connected by a plurality of cross bridges  50 , preferably at least two. Each cross bridge  50  has a protuberance  55 , and at least the cross bridge  50  closer to the axis  45  has another protuberance  60 . A protuberance  55  points toward the planes A-A′ (top half of a packing unit  10 ) and B-B′ (bottom half of a packing unit  10 ). A protuberance  60  preferably points parallel to the axis  45  but may lie along the plane of the half of the loop  15  to which it is connected. 
     The cross bridges  50  preferably have a rectangular cross section, and are disposed to circumferentially connect the two halves of the loops. The outer cross bridge  50  is approximately ¾ inch from (above or below) the exterior ring  25 , and has a width of approximately 0.063 inch, a height of approximately {fraction (5/32)} inch, and a length of approximately ½ inch. The inner cross bridge  50  is approximately 1 inch from (above or below) the exterior ring  25 , and has a width of approximately 0.063 inch, a height of approximately ⅛ inch, and a length of approximately ⅜ inch. 
     The protuberances  55  preferably emerge from the cross bridges  50  as either square or rectangular posts, and end as chisel points. The protuberances  55  from the outer cross bridges  50  preferably have a width of approximately {fraction (1/16)} inch and a length of approximately 0.25 inch. The protuberances  55  from the inner cross bridges  50  preferably have a width of approximately {fraction (1/16)} and a length of approximately 0.125 inch. 
     The protuberances  60  preferably emerge from the cross bridges  50  as round posts with flat ends, and are preferably approximately ⅛ inch high cones having a circular base of approximately 0.085 inch diameter and a circular top of approximately {fraction (1/16)} inch diameter. 
     The cross section of the filament structure of a loop  15  is preferably rectangular, with the width being the narrower dimension. As shown in FIG. 6, which is a side view of a loop  15 , and FIG. 7, which is a view of the intersection of the loop halves, the loop halves  15 A and  15 B have interior ends  15 A 1  and  15 B 1 , respectively, which are closer to the axis  45 , and exterior ends  15 A 2  and  15 B 2 , respectively, which are farther from the axis  45 . The interior ends  15 A 1  and  15 B 1  of a loop are offset by the width of the loop. Therefore, the loop halves  15 A and  15 B slightly overlap at their ends so that a continuous loop  15  is formed. This offset provides additional strength. The ends  15 A 1  and  15 B 1  are preferably tapered toward the overlapped section. Similarly, the exterior ends  15 A 2  and  15 B 2  of a loop are offset by the width of the loop, the loop halves  15 A and  15 B slightly overlap at their ends so that a continuous loop  15  is formed, and the ends  15 A 2  and  15 B 2  are preferably tapered toward the overlapped section. 
     In the preferred embodiment, there are twelve loops  15 . Because of the offsets and the opposite angles of adjacent loops, the interior ends of the top halves of two adjacent loops which are connected by cross bridges  50  will be close or touching, as indicated by  100  in FIG.  2 . Conversely, the interior ends of the top halves of two adjacent loops which are not connected by cross bridges  50  will be farther apart, as indicated by  105 . Similarly, the interior ends of the bottom halves of two adjacent loops which are connected by cross bridges  50  will be close or touching and the interior ends of the bottom halves of two adjacent loops which are not connected by cross bridges  50  will be farther apart. Thus, if twelve loops  15  are used, there will be six areas  100  and six areas  105  on the top half of the packing unit  10 , and the same number on the bottom half of the packing unit  10 . 
     The interior support  75  (FIG. 2) comprises a central circular area  80 , radial arms  85 , preferably at least three, a circular band  90 , and protuberances  95  (FIG.  1 ). The interior support  75  preferably has a thickness of approximately 0.060 inch, an inner radius of approximately 0.437 inch, and a height to match the height of the radial arms  85 . The central area  80  preferably has a radius of approximately ⅛ inch and a height to match the height of the radial arms  85 . 
     The radial arms  85  are interposed between the center area  80  and the band  90 , and have a width of approximately 0.075 inch, and a height of approximately ⅛ inch. The band  90  connects to, and is part of, the loops  15  where the interior ends  15 A 1  and  15 B 1  overlap. The band  90  may be considered to be a plurality of arc segments which connect the interior points of adjacent loops. 
     The protuberances  95  are preferably placed at every other area  105  on the top half of the packing unit  10  and at every other area  105  on the bottom half of the packing unit  10 . Thus, there are three protuberances  95  on the top half and three protuberances  95  on the bottom half. A protuberance  95  encompasses an arc and may be viewed as a curved rectangular piece, with the curve matching the radius of the circular band  90 , and extending coaxially with the axis  45 . Each protuberance  95  preferably ends with a smaller, trapezoidal, flat-ended protuberance  110 . Each protuberance  95  preferably has a length of approximately ¼ inch, a height of approximately ¾ inch, and a thickness matching the thickness of the interior support  75 . The smaller protuberance  110  preferably has a height of ⅛ inch and a top length of {fraction (3/32)} inch. 
     The exterior ring  25  (FIG. 2) preferably has thickness of approximately 0.060 inch, a depth of approximately 0.085 inch, and an inner radius of approximately 1.766 inch. 
     The exterior ring  25  has a plurality of coaxial protuberances  65  which are parallel to the axis  45 . The coaxial protuberances  65  on one side  25 A of exterior ring  25  are preferably offset with respect to the protuberances  65  on the other side  25 B of exterior ring  25 , such as shown by protuberances  65 A and  65 B in FIG.  1 . The protuberances  65  are preferably round or conical posts with flat ends, and have a base radius of approximately 0.085 inch, a top radius of approximately {fraction (1/16)} inch, and a height of approximately ⅛ inch. 
     The exterior ring  25  also has a plurality of radial protuberances  70  (FIG.  2 ). The protuberances  70  are preferably trapezoidal shaped or flat ended teeth, and have a base width of approximately {fraction (3/16)} inch, a top width of approximately {fraction (9/64)} inch, and a length of approximately {fraction (11/64)} inch. The thickness of a protuberance  70  preferably matches the thickness of the exterior ring  25 . The protuberances  65  preferably lie along the same radials as the protuberances  70 . 
     The protuberances of the loops  15 , the exterior ring  25 , the cross bridges  50 , and the interior support member  75  thus provide a large number of interstitial holdup points. 
     Nesting occurs with prior art packing units when one packing unit becomes positioned directly above another packing unit. The units may then rotate axially until the peaks of one unit match the dips in the other unit. The units will then nest, which decreases the fluid flow and increases the pressure drop through the packing column. Consider now the packing units  10  of the present invention. When one packing unit  10  becomes positioned directly above the other packing unit  10 , the numerous protuberances will contact each other and prevent rotation of the units. It will also be noted that, due to the offset of the loops  15  and the angles of the loops  15 , the protuberances  95  on the top half of the packing unit  10  do not lie directly above the protuberances  95  on the bottom half of the packing unit  10 . Thus, even if the packing units  10  are directly lined up, so that peaks of one unit match the dips in the other unit, the protuberances  95  will contact each other and prevent or significantly limit nesting. Therefore, the protuberances, the angles of the planes of the loops  15 , the exterior ring  25 , and the interior support member  75  act together to provide a packing unit which is very resistant to nesting or interlocking. 
     If a force is applied to the top of a packing unit  10 , the loops, cross members, ribs, and interior support will redistribute the force among the various components. If a force is applied laterally to a packing unit  10 , the exterior ring, the loops, the cross bridges, and the interior support will redistribute the force among the various components. Thus, the loops, the ribs, the exterior ring, the cross bridges, and the interior support act together to provide a packing unit which has great physical strength and is highly resistant to crushing. 
     It will be appreciated that the number of loops, the offset of a loop, the angles of the loops, and the number and type of ribs, cross bridges, protuberances, cross sections of the various components, and ends of the various components, may be varied without departing the scope of the present invention. Also, modifications and alterations of the present invention, such as adding nicks, notches, indentations, or other abrupt surface discontinuities, will occur to others upon reading this specification. Accordingly, all such modifications and alterations are included insofar as they come within the scope of the claims or the equivalence thereof.