Abstract:
A column for distillation or fluid-fluid separation is oriented at an angle to the horizontal other than vertical to provide increased transfer plate surface area within the interior of a column of determined diameter and to reduce overall height of the structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/545,847 entitled, “High Capacity Angled Tower,” filed on Feb. 19, 2004 in the United States Patent and Trademark Office. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to industrial columns and towers commonly used for reacting, distilling, separating, and extracting multiple components. More particularly, the present invention increases the capacity of industrial columns and towers through the acutely angular installation of the column or tower.  
         [0005]     2. Description of the Related Art  
         [0006]     Distillation is a widely applied separation technology. Distillation is continually affected by rising energy costs, thereby making increases in efficiency desirable. Commercially-practiced distillation methods operate on differences in boiling points between liquids, separating chemicals by the difference in how easily the chemicals vaporize. Distillation is ideal when the mixture is comprised of chemicals with distinct and separate boiling points. Distillation manipulates varying volatilities of components of a process fluid by applying and removing heat under high pressure or vacuum. The application and removal of heat fractionates individual components from the process fluid.  
         [0007]     A process fluid is introduced to the distillation column and heat is gradually applied. As heat is applied to the column, volatile components in the liquid begin to vaporize and ascend to the top of the column. As the vapor ascends to the top of the column, the vapor interacts with the descending condensed liquid, thereby providing interaction between the liquid and vapor phases. Separation between components is enhanced when there is greater contact between the vapors and the liquids. Once the vapors reach the top of the distillation column, the vapor can be partitioned away from the remaining process fluid through outlet lines positioned proximate the top of the distillation column.  
         [0008]     Liquid-liquid extraction is widely applied for many industrial purposes, including food, chemical, pharmaceutical, and refining. Liquid-liquid extraction is ideal for purification of heat sensitive materials and for recovery of products from reactions. Liquid-liquid extraction is extensively used in the hydrocarbon industry.  
         [0009]     While distillation focuses on the boiling points of liquids, liquid-liquid extraction focuses on chemical structure. Liquid-liquid extraction operates on mass transfer between two or more immiscible phases. A first fluid solution is contacted with a second immiscible fluid that exhibits an affinity towards one or more components in the first fluid solution. The immiscible liquid extracts the components from the first fluid solution. The components in the component-bearing immiscible fluid are not as tightly bound to the immiscible fluid, thereby permitting subsequent component separation. The effectiveness of the extraction is related to the degree of contact between the immiscible phases. An increase in contact results in an increase in extraction. Therefore, various improvements directed towards greater contact within the column have yielded greater extraction results.  
         [0010]     The vapor handling capacity of a column or tower is generally proportional to the active area of the trays. The active area is defined as the cross-sectional area through which the upward flowing vapor passes. Therefore, previous attempts in the industry to increase the capacity of columns or towers have included improvements to the internal components, or more specifically, increasing the active area of the column or tower. Despite the changes made to internal components, towers and columns have consistently been installed in a vertical orientation. Due to this orientation, the walls of the column or tower are necessarily relatively thick to withstand high force wins. Further, a substantial subterranean foundation is needed to provide stability to the vertical column or tower in high force winds or earthquakes.  
         [0011]     One alternative known in the art for increasing the capacity of a column or tower involves increasing the number of fractional trays. Mass transfer occurs when a liquid phase contacts the vapors on the trays. Increasing the number of fractional trays throughout the column increases the interaction between the liquid and vapor phases, thereby increasing the mass transfer between the liquid and vapor phases. While increasing the number of trays in the column is beneficial, the increases in capacity are limited. A specific spacing between the trays is required to facilitate proper operation of the column. If the trays are too close together or too far apart, the column may flood, thereby terminating throughput. Consequently, an increase in the number of trays necessarily increases the height of the column. Depending on restrictions in space and expense, increasing the number of trays may not be feasible.  
         [0012]     Another alternative for increasing the capacity of a column is to increase the column diameter. By increasing the column diameter, the surface area of the trays is effectively increased, resulting in a larger active area for interaction between the vapors and liquids.  
         [0013]     Previous attempts at modifying downcomer design have also increased the capacity of an industrial column. Downcomers facilitate movement of liquids between the trays. Trays are alternately installed throughout the contactor, wherein one portion of the tray is fixedly attached to the column in a horizontal orientation, and a second portion of the tray is free. Downcomers extend vertically downward from the free end of each tray. The position of the downcomer can affect the overall capacity of the column. Downcomers introduce inactive area within the column, wherein the species within the column do not interact. Recent improvements in the art have included modifying downcomer design to convert the inactive area into an active area, thereby increasing the overall active area. Attempts have included hanging downcomers, wherein the area under the downcomer is made into an active area, either with perforated holes or directional valves. While modifying downcomer design has resulted in increased capacity, installation and maintenance of hanging downcomers is difficult. Further, improper installation and maintenance can actually decrease the overall capacity of the column or tower.  
       BRIEF SUMMARY OF THE INVENTION  
       [0014]     One object of the present invention is to increase the capacity of columns or towers. Another object of the present invention is to reduce the amount of reinforcement required for tower walls and subterranean foundations to provide protection against high winds and earthquakes. Yet a further object of the invention is to provide a tower that is easy to install and maintain.  
         [0015]     Accordingly, it is an object of the present invention to increase the capacity of industrial towers and columns; 
        increase the active area of the trays;     facilitate installation and maintenance;     reduce tower wall thickness;     reduce required foundations;     reduce stress from earthquake and wind.        
 
         [0021]     A column for distillation or fluid-fluid separation is oriented at an angle to the horizontal other than vertical to provide increased transfer plate surface area within the interior of a column of determined diameter and to reduce overall height of the structure. Other features and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is a cross-sectional view of an installed industrial tower.  
         [0023]      FIG. 2  is a cross-sectional view of an industrial tower.  
         [0024]      FIG. 3  is an exploded view of an industrial tower.  
         [0025]      FIG. 4  is a cross-sectional view of an installed prior art vertical tower.  
         [0026]      FIG. 5  is a cross-sectional view of an industrial tower, depicting diameter and the major axis of the transfer plate.  
         [0027]      FIG. 6  is a top view of a transfer plate. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0028]      FIG. 1  depicts industrial tower  100  installed on foundation  50 . Industrial tower  100  is comprised of tower top  110 , tower bottom  120 , and tower shell  130 .  
         [0029]     Tower shell  130  can be of any shape but is preferably a hollow cylinder. Tower shell  130  can be made of stainless steel, carbon steel, or other material known in the art. Tower shell  130  has shell interior surface  131  and shell exterior surface  132 . Shell interior surface  131  defines a cavity throughout tower shell  130 . Tower shell  130  terminates at shell first terminal end  136  and shell second terminal end  138 . Closed end surfaces tower top  110  and tower bottom  120  are provided proximate shell first terminal end  136  and shell second terminal end  138 , respectively.  
         [0030]     Industrial tower  100  is angularly installed onto foundation  50  by affixing a plurality of support members  190  to industrial tower  100 . Downward facing tower shell side  133  forms acute tower angle  140  with respect to the horizon. Conversely, upward facing tower shell side  134  forms obtuse angle  155  with respect to the horizon. By installing industrial tower  100  at an angle offset from vertical, the cross-sectional area of tower  100  is increased, thereby increasing the active area.  
         [0031]     A plurality of transfer plates  200  are fixedly attached to shell interior surface  131 . Each transfer plate  200  is planar and is configured to be received within shell interior surface  131 , such that a section of the perimeter of transfer plate  200  is circumscribed by shell interior surface  131 . Transfer plate  200  incorporates a plurality of perforated holes (not show), which allow fluids and vapors to traverse tower  100 . In the prior art vertical tower  300 , depicted in  FIG. 4 , transfer plate  200  has a circular configuration. However, because the present invention is installed at an angle relative to tower shell  130 , transfer plate  200  may be elliptically configured at its interface with shell interior surface  131 .  
         [0032]     Transfer plate  200  can be attached through tray rings with clips (not shown) or other means known in the art. Transfer plates  200  enhance separation between the process vapor and liquid in a distillation column, and increase the extraction in a liquid-liquid extraction tower. Transfer plates  200  are typically installed in an alternating pattern, wherein a first transfer plate  200  is partially affixed to interior shell surface  131 , resulting in a first affixed plate surface  210  and a first open plate surface  212 , and an opposing second transfer plate  200 , resulting in a second affixed plate surface  210  and a second open plate surface  212 . Transfer plates  200  are installed at a uniform spacing commonly known in the art for preventing flooding of tower  100 .  
         [0033]     Angularly installed tower  100  and vertically installed tower  300  are depicted in  FIGS. 1 and 4 , respectively. Referring to  FIG. 1 , transfer plates  200  are preferably installed in a horizontal orientation. Alternatively, transfer plate  200  may be slightly inclined with respect to the horizon. Transfer plate  200  forms transfer plate acute angle  250  with respect to upward facing tower shell side  134 . In the preferred embodiment, transfer plate acute angle  250  is the same angle as tower acute angle  150 . Similarly, referring to  FIG. 4 , vertical tower transfer plate  220  is preferably installed in a horizontal orientation, thereby forming right angle  222  with respect to vertical tower shell  310 . Thus transfer plate  200  (seen in  FIG. 1 ) is elongated in comparison to vertical tower transfer plate  220  (seen in  FIG. 4 ), thereby resulting in greater surface area for transfer plate  200 . By increasing the surface area of transfer plates  200 , the capacity of industrial tower  100  is increased.  
       EXAMPLE  
       [0034]     An angularly installed industrial tower  100  with diameter  180  and major axis  210  of transfer plate  200  is shown in  FIGS. 5 and 6 . Diameter  180  extends across industrial tower  100  and is perpendicular with respect to tower shell  130 . Major axis  210  extends across industrial tower  100  in a diagonal orientation with respect to tower shell  130 , and parallel with respect to the horizon. Diameter  180  forms a right angle with tower shell  130 . Diameter  180  intersects major axis  202  at intersection point  270 , thereby forming transfer plate acute angle  250  Thus, a right triangle is formed between diameter  180 , major axis  202 , and tower shell segment  139 .  
         [0035]     The surface area of transfer plate  200  can be calculated as detailed below. As previously stated, transfer plate  200  is elliptical. Therefore, transfer plate  200  has major axis  202  and minor axis  204 , both seen in  FIG. 6 . The area of an ellipse can be calculated by multiplying one-half the major axis, one half the minor axis, and pi. Thus: 
 
Area of ellipse=(π)(major axis/2)(minor axis/2). 
 
 Minor axis  204  is equal to diameter  180 . Therefore: 
 
Area of ellipse=(π)(major axis/2)(diameter/2). 
 
 When there is a known angle, major axis  202  can be determined from the following equation: 
 
(major axis)=(diameter)/((2)(sin Θ)). 
 
 Thus, the equation to find the surface area of transfer plate  200  becomes: 
 
Area of ellipse=(π)((diameter)/(2)(sin Θ))(diameter/2)=((π)(diameter 2 ))/((4)(sin Θ)). 
 
         [0036]     Table 1 summarizes the surface area for transfer plate  200  when the tower is installed at various angles.  
                                     TABLE 1                       Angle of Tower   Surface Area (ft. 2 )   Percent Increase                                90°   12.56    0%       40°   19.48    55%       38°   20.40    62%       30°   25.13   100%       25°   29.85   137%                  
 
         [0037]     The results in Table 1 show that as the angle of industrial tower  100  becomes more acute with respect to the horizon, the surface area of transfer plate  200  increases. The percent increase is measured against a vertical tower installed at a 90° angle, which is currently practiced in the industry.  
         [0038]     The foregoing description of the invention illustrates a preferred embodiment thereof. Various changes may be made in the details of the illustrated construction within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the claims and their equivalents.