Abstract:
A reactor produces a gas-in-liquid emulsion for providing increased interfacial contact area between the liquid and the gas for improved reaction of the gas with the liquid, or more rapid solution or reaction of a difficulty to dissolve or immiscible gas in or with a liquid. The reactor is suitable for a continuous or batch type process. Rotor and stator cylindrical members are mounted for relative rotation one to the other and have opposing surfaces spaced to form an annular processing passage. The gap distance between the opposing surfaces and the relative rotation rate of the cylindrical members are such as to cause formation of a gas-in-liquid emulsion of the gas in the liquid, as the liquid and gas pass through the processing passage.

Description:
[0001]    This application is a divisional of U.S. application Ser. No. 09/894,996, filed Jun. 27, 2001, which claims the benefit of the prior filing date of U.S. provisional patent application No. 60/214,538, filed Jun. 27, 2000, herein incorporated by reference in their entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to materials processing involving a chemical and/or a physical action(s) or reaction(s) of a component or between components. More specifically, the present invention produces a gas-in-liquid emulsion in a reactor to continuously process relatively large quantities of materials.  
           [0004]    2. General Background and State of the Art  
           [0005]    Apparatus for materials processing consisting of coaxial cylinders that are rotated relative to one another about a common axis, the materials to be processed being fed into the annular space between the cylinders, are known. For example, U.S. Pat. No. 5,370,999, issued 6 Dec. 1994 to Colorado State University Research Foundation discloses processes for the high shear processing of a fibrous biomass by injecting a slurry thereof into a turbulent Couette flow created in a “high-frequency rotor-stator device”, this device having an annular chamber containing a fixed stator equipped with a coaxial toothed ring cooperating with an opposed coaxial toothed ring coupled to the rotor. U.S. Pat. No. 5,430,891, issued 23 Aug. 1994 to Nippon Paint Co., Ltd. discloses processes for continuous emulsion polymerization in which a solution containing the polymerizable material is fed to the annular space between coaxial relatively rotatable cylinders.  
           [0006]    U.S. Pat. No. 5,279,463, issued 18 Jan., 1994, and U.S. Pat. No. 5,538,191, issued 23 Jul. 1996, both having the same applicant as the present invention, disclose methods and apparatus for high-shear material treatment, one type of the apparatus consisting of a rotor rotating within a stator to provide an annular flow passage. U.S. Pat. No. 5,538,191, in particular, at column 13, line 37, describes using the invention as a gas/liquid chemical reactor by enveloping the greater part of the liquid that clings to the periphery of the spinning rotor with a body of the reactant gas. The high peripheral velocity of the wetted, spinning rotor causes the gas to be in a highly turbulent state of surface renewal at its contact interface with the liquid film. However, this gas/liquid reaction method provides a relatively small gas/liquid contact area and is prone to considerable back-mixing (mixing in the longitudinal, axial or general flow direction) of the gas component thus providing an undesirably large residence time distribution (RTD), impairing the overall efficiency of the process.  
           [0007]    Sparging gasses through liquids for reacting the gasses with the liquids is also known in the prior art, but also fails to provide adequate interfacial contact area between the liquid and gas.  
           [0008]    It would be desirable to provide a large interfacial contact area between a liquid and a gas in an efficient continuous or batch type process.  
         SUMMARY OF THE INVENTION  
         [0009]    Accordingly, an object of the present invention is to provide a method and apparatus for producing a gas-in-liquid emulsion for providing increased interfacial contact area between the liquid and the gas for improved reaction of the gas with the liquid, or more rapid solution or reaction of a difficulty soluble or immiscible gas in or with a liquid. This invention provides a superior, more economical and more efficient way of contacting gases with liquids for the purpose of effecting reactions between them to be carried out as a continuous or batch type process. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a part elevation, part longitudinal cross sectional view of a complete reactor of the present invention;  
         [0011]    [0011]FIG. 2 is a transverse cross-sectional view of a reactor showing the cylindrical members in a concentric configuration with gas and liquid inlets leading to the processing chamber;  
         [0012]    [0012]FIG. 3 is a cross-sectional view of an eccentrically mounted embodiment of the reactor in which the longitudinal axes of the cylindrical members are displaced to give an annular passage that varies in radial width around its circumference, the reactor including a series of gas inlets along its length;  
         [0013]    [0013]FIG. 4 is a cross sectional view of an eccentrically mounted embodiment of the reactor similar to FIG. 3, but showing a gas inlet at the top of the reactor and fluid inlets along the bottom of the reactor; and  
         [0014]    [0014]FIG. 5 is a diagrammatic representation of the gas-in-liquid emulsion further illustrating incident white light and light scattered by the gas bubbles. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    A reactor  8  is illustrated by FIGS. 1-4, and described in greater detail in U.S. patent Ser. No. 09/802,037 entitled “Method and Apparatus for Materials Processing”, filed Mar. 7, 2001 and U.S. Pat. No. 5,538,191 entitled “Methods and Apparatus for High-Shear Material Treatment” both by the applicant of the present invention and both of which are hereby incorporated by reference in their entirety into the present disclosure. An annular cross section processing chamber  44  having an annular gap is formed between an outer cylindrical member or cylindrical tube  30  comprising a stator and a cylindrical rotor or inner cylindrical member  42 . Liquid and gas enter the processing chamber  44  through inlets  14 . The cylindrical members  30 ,  42  rotate relative to each other producing a shear force on the liquid, gas and any other reactants as they are pumped through the processing chamber and out an outlet  52  at the downstream end of the processing chamber  44 .  
         [0016]    Turning to FIGS. 1 and 2 in particular, reactants are fed from supply tanks  10 ,  16 ,  20 , respectively. Also shown are metering pumps  12  and  18  leading from the supply tanks  10 ,  16  and into the inlet  14 . The reactants can be aqueous solutions and a gas such as carbon dioxide. The reaction can occur at room temperature and atmospheric pressure for example, although other temperatures and pressures can be chosen as appropriate.  
         [0017]    The reactor comprises a baseplate  22  on which is mounted rotor bearing supports  24 , stator supports  26  and a variable speed electric drive motor  28 . The cylindrical member  30 , comprising the apparatus stator, is mounted on the supports  24 . A rotor shaft  40  extends between the supports  24  and is supported thereby, one end of the shaft being connected to the motor  28 . The shaft  40  carries the cylindrical member  42 , comprising the apparatus rotor. The processing chamber  44  is formed between the inner cylindrical surface  46  of the cylindrical member  30  and the outer cylindrical surface  48  of rotor  42  and face body  51 . The ends of the chamber are closed against leakage by end seals  50  that surround the shaft  40 .  
         [0018]    In the embodiment of FIGS. 1 and 2 the cylindrical member  42  is shown with its axis of rotation roughly coincident, or concentric, with the longitudinal axis of the cylindrical member  30 . The processing chamber  44  is shown having a radial dimension of H.  
         [0019]    In another embodiment, as illustrated in FIGS. 3 and 4 for example, the cylindrical member  42  has its axis of rotation not coincident with, but rather eccentric, relative to the longitudinal axis of the cylindrical member  30 . The processing chamber  44  has a smaller radial dimension G and a larger radial dimension H diametrically opposite. The processing chamber  44  is therefore circumferentially alternately convergent from the portion having the dimension H to the portion having the dimension G at which portion the surfaces  46 ,  48  are spaced a minimum distance apart and the maximum shear is obtained in the flowing material; the chamber  44  is then divergent from the portion having the dimension G to the portion having the dimension H.  
         [0020]    Rather than the horizontal orientation of FIG. 1, the reactor can be configured vertically with the outlet  52  at the top. Other orientations can be used as well. Also, other inlet and outlet configurations can be used. For example, in FIG. 3 a series of inlets  14  positioned along the length of the reactor  8  and passing through the cylindrical member  30  supply gas into the processing chamber  44 . FIG. 4 shows an embodiment in which both the inlet (not shown) and outlet  52  are disposed at the lowermost part of the cylindrical member  30 , while the gas is fed into the processing chamber  44  by a separate inlet  146 . In a general embodiment, the reactants are pumped into the inlets  14 , through the processing chamber  44  and out an outlet. The inlets  14  and outlets  52  can be at opposite ends of the length of the processing chamber  44  to allow mixing and reacting along the length of the processing chamber  44 .  
         [0021]    U.S. Provisional Application No. 60/214,538 entitled “Process for High Shear Gas-Liquid Reactions” to Holl filed on Jun. 27, 2000, which is hereby incorporated by reference in its entirety into the present disclosure, describes the use of the reactor  8  for gas/liquid reaction. The reactor emulsifies the gas into the liquid providing increased contact between the liquid and gas for more efficient reactions. The inventor of the present invention discovered that a gas-in-liquid emulsification can be created by narrowing the radial dimension between the surfaces  46 ,  48  of the processing chamber  44  while rapidly rotating the rotor cylindrical member  42  relative to the stator cylindrical member  30 .  
         [0022]    For the gas-in-liquid emulsification to occur, the radial dimension between the surfaces  46 ,  48  of the processing chamber  44  should be approximately equal to or less than the combined thickness of the two laminar boundary layers back-to-back. As the material being processed flows in the processing chamber  44  a respective boundary layer forms on each of the surfaces  46  and  48 , the thickness of which is determined by the viscosity and other factors of the material being processed and the relative flow velocity of the material over the surface. The laminar boundary layer for a fluid flowing over a flat surface along a path length x, which in the invention is taken as one circumferential flow length around the rotor surface, may be determined by the equation:  
       δ   =     4.91       N   R                               
 
         [0023]    where N RX  is the product of length x and the flow velocity divided by the kinematic viscosity.  
         [0024]    In addition to having a radial dimension requirement, the peripheral speed of the rotor cylindrical member  42  relative to the stator cylindrical member  30  should exceed approximately four meters per second for the gas-in-liquid emulsification to occur. The upper limit on the peripheral speed is determined by the application. For example, too great a speed might destroy living microbes or long molecular chains. Also, too great a speed can subject the reactor  8  to unnecessary stress and strain.  
         [0025]    The required radial dimension and peripheral speed can vary depending on conditions. The radial dimension requirement and peripheral speed required for the onset of the emulsification phenomenon can be determined experimentally for given reactants under specified conditions. The onset of this emulsification phenomenon is indicated by the appearance of a white colored turbidity of the fluid agitated in the processing chamber  44 . The stator cylindrical member  48  can, for observation purposes, be made of glass. The grayish-white to white, almost milk like turbidity  
         [0026]    supply energy into the processing chamber  44  through a port  58  and window  60  as illustrated in FIGS. 2 and 3. This use of energy is described in greater detail in U.S. patent Ser. No. 09/853,448 entitled “Electromagnetic Wave Assisted Chemical Processing” by Holl filed May 10, 2001 which is hereby incorporated by reference in its entirety into the present disclosure. The energy can also be used in combination with the Taylor-vortices free gas-in-liquid emulsion for additional reaction capabilities.  
         [0027]    Also, the cooperating surfaces  46  and  48  in FIGS. 2 and 3 can be coated with a catalyst to facilitate a chemical or biological reaction that constitutes the processing step. The catalytic material can enhance chemical, biochemical or biocidal reactions in the processing passage.  
         [0028]    Importantly, the reactor  8  can be quickly and thoroughly cleaned. Therefore, unlike the prior art, deposits forming and blocking the irradiation is not a problem. For example, even if the reactant is a sticky opaque substance, the surfaces  46 ,  48  and window  60  are easily cleaned. By running the reactor  8  with clean water for enough time for the water to pass from the inlet  14  to the outlet  52 , substances clinging to the surfaces  46 ,  48  and the window  60  are washed away. In most cases the surfaces of the processing chamber  44  are clean within five seconds. This efficient cleaning ability is due to the extremely hard sheer forces as the rotor cylindrical member  42  and stator cylindrical member  30  rotate relative to each other. In most cases, no contaminants will even form on the window  60  or surfaces  46 ,  48  of the processing chamber  44  due to the hard sheer forces pulling the materials through the reactor  8 .  
         [0029]    The gas/liquid reaction can be used in an oxygenation process, or an enzyme reaction process for example: Additionally, solids, such as catalytic powders, can be added to the processing chamber  44  to form a gas/liquid/solid emulsion to provide a gas/liquid/solid reaction which can also be enhanced by the applied electromagnetic or longitudinal pressure energy as described below.  
         [0030]    Returning to FIG. 3, the illustrated embodiment is intended for an enzyme reaction process, and the axis of rotation of the rotor cylindrical member  42  is eccentrically mounted relative to the longitudinal axis of the stator cylindrical member  30 , so that the radial processing chamber  44  differs in dimension circumferentially around the rotor. A heat exchange structure is provided having an outer casing  32  and heat exchange material  34 , since such processes usually are exothermic and surplus heat must be removed for optimum operative conditions for the microorganisms. A series of oxygen feed inlets  14  are arranged along the length of the stator and the oxygen fed therein is promptly emulsified into the broth, providing uniformly dispersed, micron-fine bubbles instead of being sparged therein with mm size bubbles of non-uniform distribution, as with conventional enzyme reaction systems. The carbon dioxide that is produced is vented from the upper part of the processing passage through a vent  56 . The reactor according to FIG. 3 is designed to operate continuously and provides a continuous and uniform CO 2  removal along the upper portion of the rotor which is constantly wetted with a film of broth of uniform mixedness of all ingredients. Also shown is the port  58  and window  60  as described with reference to FIG. 2.  
         [0031]    The apparatus of the invention is generically a reactor process and apparatus, and a reactor consists of the vessels used to produce desired products by physical or chemical means, and is frequently the heart of a commercial processing plant. Its configurations, operating characteristics, and underlying engineering principles constitute reactor technology. Besides stoichiometry and kinetics, reactor technology includes requirements for introducing and removing reactants and products, supplying and withdrawing heat, accommodating phase changes and material transfers, assuring efficient contacting among reactants, and providing for catalyst replenishment or regeneration. These issues are taken into account when one translates reaction kinetics and bench-scale data into the design and manufacture of effective pilot plants, and thereafter scale up such plants to larger sized units, and ultimately designs and operates commercial plants.  
         [0032]    While the specification describes particular embodiments of the present invention, those of ordinary skill can devise variations of the present invention without departing from the inventive concept.