Abstract:
The lower, liquid collecting section of a gas/liquid contacting column has an entrained substance depleting duct extending therearound wherein gas, for example, steam is fed by the duct into the lower section, steam depleted by gravity of liquid droplets, is deflected upwardly by deflectors in the duct through duct openings into a central, upper region of the lower section, while steam with the droplets is deflected downwardly by deflectors in the duct through other duct openings towards a liquid pool in the lower section. Any other liquid and/or solids entrained in the gas (steam) are also deflected downwardly in this manner.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention to a gas/liquid contacting apparatus.  
       BACKGROUND OF THE INVENTION  
       [0002]     There are various types of gas/liquid contacting apparatus wherein liquid passing downwardly through casing is contacted therein by gas passing upwardly through perforated trays which partition the casing at different levels.  
         [0003]     In one type of gas/liquid contacting apparatus the liquid flows across the trays and is frothed thereon by gas permeating the tray perforations, see, for example, U.S. Pat. Nos. 2,005,316, dated Jun. 18, 1935, F. N. Hall, 3,022,316, dated Feb. 20, 1962, M. H. Kotzebue, and 5,895,608, dated Apr. 20, 1999, A. T. Lee, K. Wu and L. Burton.  
         [0004]     In another type of gas/liquid contacting apparatus ordered or randomly distributed packing elements of packed beds are supported by the trays. These beds increase the surface contact area between gas and liquid in the apparatus. The packed beds may be catalyst packed beds, see, for example, U.S. Pat. No. 4,514,377, dated Apr. 30, 1985.  
         [0005]     There is a problem with a gas/liquid contacting apparatus in that liquid droplets and/or solids entrained in gas fed to the apparatus, particularly when the gas is at a high velocity, can prevent effective passage of gas upwardly through, for example, tray perforations and packings, and have other detrimental effects on the gas/liquid contact, see, for example, column 1, line 66, to column 2, line 12, of U.S. Pat. No. 5,895,608, referred to above. The liquid droplets and/or solids may be in the form of water or other liquids in steam or other gases, and solid contaminants in particulate form entrained in steam or other gases.  
         [0006]     U.S. Pat. No. 5,895,608, dated Apr. 20, 1999, FIG. 1, shows a vapor feed line or reboiler return line, designated 32, which has a downwardly facing, vapor outlet which will, to a limited extent, deposit liquid droplets entrained in the vapor into liquid therebelow. However, no steam/entrained liquid droplets separation takes place in the vapor feed line, with entrained substance depleted steam exiting the feed line by a different outlet than the separated droplets, and so a significant amount of liquid droplets remains entrained in the steam which passes upwardly from the feed line.  
         [0007]     There is a need for a gas/liquid contacting apparatus wherein an entrained substance separator, gas distributor, is provided in a lower, liquid collecting section thereof, which will, 
        i) separate a significant amount of entrained substances from the gas steam,     ii) provide different exits for the entrained substance depleted gas exiting from the distributor than those for separated, gas entrained substances exiting therefrom, and     iii) distribute the gas more evenly in the lower, liquid collecting section.        
 
       SUMMARY OF THE INVENTION  
       [0011]     According to the present invention there is provided a gas/liquid contacting apparatus, comprising, 
        a) an upwardly extending column having an interior comprising, an upper section, a gas/liquid permeable, gas/liquid contacting, intermediate section, and a lower, liquid collecting section,     b) liquid inlet means to, and gas outlet means from, the upper section,     c) liquid outlet means from, and gas inlet means to, the lower section, and     d) an entrained substance depleting, gas distributing assembly in the lower section, the assembly comprising, 
            i) a gas conveying duct connected to the gas inlet and having an interior that decreases in cross section downstream from the gas inlet, the duct extending around at least a major portion of the lower section, and having entrained substance depleted gas outlets, at spaced positions therealong, from inner, upwardly extending wall portions thereof, and entrained substance concentrate gas outlets, at spaced positions therealong, from inner, downwardly extending lower wall portions thereof, and     ii) for each entrained substance depleted gas outlet, a gas deflector for directing gas flow from that gas outlet inwardly and upwardly in the lower section, and     iii) for each entrained substance concentrate gas outlet an entrained substance concentrate gas deflector for directing entrained substance concentrate gas flowing from that entrained substance concentrate gas outlet towards a lower portion of the lower section.    
               
 
         [0019]     The entrained substance concentrate gas outlets may be spaced along the duct at positions between the gas outlets.  
         [0020]     The gas conveying duct may be divided into two lengthwise extending portions by being connected at an intermediate position therealong to the gas inlet, with the duct interior decreasing in cross-section in both duct portions downstream from the gas inlet, and the entrained substance depleting, gas distributing assembly may further comprise a flow splitter for splitting the flow of gas entering the duct into gas streams for both duct portions.  
         [0021]     The gas conveying duct may comprise a base wall extending inwardly from, and around at least a portion of an inner side of the column, a top wall spaced above the base wall and extending inwardly from, and around, the inner side of the column, with the inner, upwardly extending wall portion inclining downwardly from an inner edge of the top wall, towards the center of the lower section, and the inner, downward extending wall portion inclining upwardly from the level of the base to a lower edge of the inner, upwardly extending wall portion.  
         [0022]     The inner, upwardly extending wall portion may comprise a series of plates with inverted V-shaped gas outlets between adjacent plates forming the entrained substance depleted gas outlets, and the inner, downwardly extending wall portion comprises a series of plates with V-shaped gaps between adjacent plates forming the entrained substance concentrate gas outlets.  
         [0023]     Each entrained substance depleted gas deflector may comprise an upwardly extending triangular plate joined by an upper sloping side to an upstream side of an inner, upwardly extending wall portion, and by a lower, sloping side to a downstream side of an inner, downwardly extending wall portions, and each entrained substance concentrate gas deflector may comprise a downwardly extending triangular plate joined by an upper sloping side to a downstream side of an inner, upwardly extending wall portion and by a lower sloping side wall to an upstream side of an inner, downwardly extending wall portions.  
         [0024]     The entrained substance depleted gas deflectors and the entrained substance concentrate gas deflectors may be curved to sweep entrained substance depleted gas or entrained substance concentrate gas towards their respective outlets.  
         [0025]     The duct may extend along a circular path.  
         [0026]     Preferably, the entrained substance depleted gas outlets and the entrained substance concentrate gas outlets are gas flow constricting gas outlets.  
         [0027]     In this patent specification, entrained substances means any entrained substances, in liquid and/or solid form, entrained in a gaseous stream which may comprise one or more gases and/or liquids in vapor form. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     In the accompanying drawings which illustrate, by way of example, embodiments of the present invention.  
         [0029]      FIG. 1  in a schematic side view of a gas/liquid contacting apparatus,  
         [0030]      FIG. 2  is a sectional plan view along II-II,  FIG. 1 ,  
         [0031]      FIG. 3  is a perspective view of an entrained substance depleting, gas distributing means in the apparatus shown in  FIGS. 1 and 2 ,  
         [0032]      FIG. 4  is a schematic side view of a different gas/liquid contacting to that shown in  FIG. 1 , and  
         [0033]      FIG. 5  is a perspective view of an entrained substance depleting, gas distributing assembly in the apparatus shown in  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     In  FIG. 1  to  3 , there is shown a gas/liquid contacting apparatus, which may be, for example, a hydrocarbon fractionating apparatus, comprising, 
        a) an upwardly extending column  1  having an interior comprising, an upper section  2 , a gas/liquid permeable, gas/liquid contacting, intermediate section  4 , and a lower, liquid collecting section  6 ,     b) liquid inlet means  8  to, and gas outlet means  10  from, the upper section  2 ,     c) liquid outlet means  12  from, and gas inlet means  14  to, the lower section  6 , and     d) an entrained substance depleting, gas distributing assembly, generally designated  16 , in the lower section  6 , the assembly  16  comprising, 
            i) a gas conveying duct  18  ( FIG. 3 ) connected to the gas inlet  14 , and having an interior  19  that decreases in cross sectional area downstream from the gas inlet  14 , the duct  18  extending around at least a major portion of the lower section  6 , and having entrained substance depleted gas outlets  20 , at spaced positions therealong, from inner, upwardly extending wall portions  22 , thereof, and entrained substance concentrate gas outlets  24 , at spaced positions therealong, from inner, downwardly extending wall portions  26 , thereof, and    
            ii) for each entrained substance depleted gas outlet  20 , an entrained substance depleted gas deflector  28  for directing gas flow from that gas outlet  20  inwardly and upwardly in the lower section  6 , and     iii) for each entrained substance concentrate gas outlet  24  an entrained substance concentrate gas deflector  30  for directing entrained substance concentrate gas flowing from that entrained substance concentrate gas outlet inwardly and downwardly in the lower section  6 .        
 
         [0042]     The entrained substance concentrate gas outlets  24  are spaced along the ducting  18  at positions between the entrained substance depleted gas outlets  20 .  
         [0043]     In this embodiment of the present invention, the duct  18  is divided into two lengthwise extending portions  32  and  34  by being connected at an intermediate position therealong to the gas inlet  14 . The duct interior  19 , decreases in cross-sectional area in both downstream directions, that is in both duct portions  32  and  34 , from the gas inlet  14 , and the entrained substance depleting, gas distributing assembly  16  further comprises a flow splitter  36  for splitting the flow of gas entering the duct  18  into gas streams for both directions, that is into both casing portions  32  and  34 .  
         [0044]     As will be seen from  FIG. 3 , the duct  18  comprises a base wall  38  extending inwardly from, and around a portion of an inner side of the column  1 , a top wall  40  spaced above the base wall  38  and extending inwardly from, and around, the inner side of the column  1 , with the inner, upwardly extending wall portion  22  inclined downwardly from an inner edge of the top wall  40 , towards the center of the lower section  6 , and with the inner, downwardly extending wall portion  26  inclined upwardly from the level of an inner edge of the base wall  38  to a lower edge of the inner, upwardly extending wall  22 .  
         [0045]     The inner, upwardly extending wall portion  22  comprises a series of plates, such as those designated  46 , with the first two, joined to the flow splitter  36  and from that position inverted V-shaped gaps are provided between adjacent plates  46  as the entrained substance depleted gas outlets  20 .  
         [0046]     The inner, downwardly extending wall portion  26  comprises a series of plates, such as those designated  48 , with the first two joined to the flow splitter  36  and from that position V-shaped gaps and provided between adjacent plates  48  as the entrained substance concentrate gas outlets  24 .  
         [0047]     The gas deflectors  28  each comprise upwardly extending triangular plates joined by an upper sloping side to an upstream side of the plates  46  and by a lower sloping side to a downstream side of the plates  48 .  
         [0048]     The entrained substance concentrate gas deflectors  30  each comprise downwardly extending triangular plates joined by an upper sloping side to a downstream side of the plates  46  and by a lower sloping side to an upstream side of the plates  48 .  
         [0049]     The gas deflectors  28  and the entrained substance concentrate gas deflectors  30  are curved, in this instance with a series of bends, to sweep gas or entrained substance towards their respective outlets  20  and  24 .  
         [0050]     The entrained substance depleting and gas distributing assembly  16  is attached to the column  1  by brackets  50  and  52 .  
         [0051]     In this embodiment of the present invention, the permeable, gas/liquid contacting, intermediate section ( FIGS. 1 and 2 ) comprises a series of perforated trays  54  and  60 , and downcomers  62  to  68 .  
         [0052]     In operation, liquid is distributed over the top tray and descends to collect in the lower section  6 , and exit therefrom by liquid outlet means  12 , while gas is fed into the column  1  by gas inlet means  14  and ascends in the column  1  to exit therefrom by gas outlet  10 .  
         [0053]     The liquid descends in the column  1  by flowing across the trays  54  and  60  in the directions of arrows A and B, while the downcomers  62  and  68  maintain a level of liquid on the trays  54  to  60  and form liquid seals so that ascending gas passes upwardly through the perforated trays  54  to  60 .  
         [0054]     The gas passing up through the perforated trays  54  to  60  froths the liquid flowing across the trays  54  to  60  and in this manner is brought into intimate contact with the liquid.  
         [0055]     Liquid exiting from the column  1  forms a pool  70  ( FIG. 1 ) in the lower, liquid collecting section  6 , which forms a liquid seal with the downcomer  68 .  
         [0056]     The apparatus shown in  FIG. 1  may be used, for example, as a fractionating column, or a distillation column wherein oil is the liquid fed to the liquid inlet means  8  and steam is the gas fed to gas inlet means  14 . The steam fed to the gas inlet means  14  usually contains entrained water droplets, and may contain other entrained substances in liquid or solid form. These entrained substances reduce the efficiency of the column by blocking and/or reducing the effective areas of tray perforations, and reducing contact between the liquid and the gas. This is an even greater problem when bubble caps (not shown) are provided over the tray perforations.  
         [0057]     With the present invention, steam fed to the liquid inlet means  8  is split by the flow splitter  36  into two streams to flow around the duct  18  ( FIG. 3 ) as two streams flowing in opposite directions. As the streams flow downstream around the duct  18  entrained water droplets and any other entrained liquid or solid substances tend to gravitate towards a lower portion of the stream, or collect on the wall of the duct  18  and drain downwardly, leaving entrained substance depleted steam to be swept by the gas deflectors  28  out of the duct  18  and upwardly across the underside of the perforated tray  60 . The entrained substances which have gravitated to a lower portion of the duct  18 , and are concentrated in a portion of the steam flowing along a lower portion of the duct  18 , are swept by the entrained substance concentrate gas deflectors  30  downwardly into the liquid pool  70  ( FIG. 1 ).  
         [0058]     The gradual reduction in cross-section of the interior of the duct  18  in the direction of flow ensures a more even distribution of steam around the casing  1  with a consequent greater removal of entrained substance therefrom.  
         [0059]     It will be seen in  FIG. 1  that the assembly is immersed in the liquid pool  70 , however, in other embodiments of the present invention, as shown chain dotted, the gas inlet  14  means and the assembly  16  are above the pool  70 , and the assembly  16  only extends beneath the area covered by the perforated tray  60 .  
         [0060]     In other embodiments, as is well known in the art, the downcomer  68  terminates in a liquid trap and the assembly  16  extend underneath the trap.  
         [0061]     In other embodiments of the present invention the top wall  40  ( FIG. 3 ) of the duct  18  may be sloped so that any entrained substances collecting thereon drain away from the gas deflectors  28  towards the wall of the column  1 .  
         [0062]     In other embodiments of the present invention, the base wall  38  of the duct  18  may be sloped so that any entrained substances collecting thereon will be drained towards the entrained substance concentrate gas outlets  24  and deflectors  30 .  
         [0063]     In other embodiments of the present invention, the base wall  38  may, as shown chain dotted in  FIG. 3 , extend around the whole length of the duct  18 .  
         [0064]     In yet other embodiments of the present invention, the gas outlets  20  and the entrained substances concentrate gas outlets  24  increase in cross-sectional area in the downstream direction to more evenly distribute the flows from them into the lower, liquid collecting section  6 .  
         [0065]     In  FIGS. 4 and 5 , similar parts to those shown in FIGS.  1  to  3  are designated by the same reference numerals and the previous description is relied upon to describe them.  
         [0066]     In  FIG. 4 , the gas/liquid permeable, gas/liquid contacting section  4  comprises perforated trays  72  to  75  and packed beds  76  to  70 . The packed beds  76  to  79  may be, for example, catalyst packed beds or absorbent, or absorbent, packed beds capable of regeneration.  
         [0067]     The entrained substance depleting, gas distributing assembly, generally designated  80  is connected to a gas inlet  82  of a cylindrical column  1 , and feeds the gas tangentially into the column  1 .  
         [0068]     In  FIG. 5 , the duct  18  extends along a circular path and above the liquid pool  70 , but in other respects is similar to the duct  18  of  FIG. 3 .  
         [0069]     The gas distributing assembly  80  functions in the same manner as that described with reference to FIGS.  1  to  3 , described with reference to  FIG. 1  to  3 . However, in this embodiment of the present invention liquid permeates downwardly through the packed beds  76  to  79 , while gas passes upwardly through them.  
         [0070]     In other embodiments, when the assembly  16  is not immersed in liquid, the gas deflectors  28  are only attached to downstream sides of the upwardly extending plates  48 , with gaps between them and the next plate  48 . The entrained substance, gas deflectors  30  are only attached to downstream sides of the downwardly extending plates  46 , with gaps between them and the next plate  46 . These gaps will cause pressure drops behind the gas deflectors  28  and the entrained substance, gas deflectors  30  which deflect the gas flow along the duct  18  either upwardly towards the next gas outlet  20 , or downwardly towards next entrained substance, gas outlet  24 .  
         [0071]     Preferably, the entrained substance depleted gas outlets  20  are gas flow constricting gas outlets to enhance distribution of the depleted gas in the lower Section C.  
         [0072]     Preferably, the entrained substance concentrate gas outlets  24  are gas flow constricting gas outlets to enhance removal of entrained substance from the duct  18 .