Abstract:
A mixing apparatus for mixing two fluids immediately following contact with each other is disclosed. The mixing apparatus includes a spring-loaded ball valve separating a first fluid from a second fluid. The ball valve closes as a result of at least spring force. The ball valve opens as a result of hydraulic pressure of one of the fluids operating against the spring force. Mixing is accomplished instantaneously by dispersing one fluid in a thin pattern around the open ball valve into a stream of the other fluid.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to an apparatus that can perform dual functions of isolating and mixing two different fluids. The apparatus can be used to dilute or pre-mix one fluid with another and, when not in operation, completely isolates the two starting fluids from each other.  
           [0002]    Many processes require mixing two different fluids or diluting one fluid with another. For example, liquid polyelectrolytes (polymers) used in various water treatment and wastewater treatment processes must be diluted with water to create solutions having small concentrations, say, up to approximately 10% polymer, by weight or volume. Due to the large amount of water required to achieve this level of dilution, it is usually more cost effective to transport the polymer ingredient to the site and to dilute it with water already available at the site.  
           [0003]    The polymers to be diluted can be compositions such as polyelectrolytes, for example. Proper mixing of liquid polymers with water is not always easy. Most polymers can activate very quickly once they come into contact with water or aqueous compositions, and can form a highly viscous and sticky agglomeration if not promptly and thoroughly mixed with an appropriate amount of water. A positive means of mixing must be implemented to dilute the polymer effectively. The viscosity of a particular solution can vary in direct proportion to the percentage of polymer in the solution. In other words, as the percentage of polymer in the solution is increased, the viscosity of the solution is also increased, and vice versa. Inadequate or slow mixing of the liquid polymer with the water can result in excessive and undesirable coagulation of the mixture and consequent clogging or obstruction of system piping and components. Clogging can be so significant that a system might be rendered inoperable until it is cleaned and the obstruction is cleared.  
         SUMMARY OF THE INVENTION  
         [0004]    The apparatus of the invention provides a positive seal to avoid completely any possibility of polymer leakage into any part of a water or aqueous solution line whenever the polymer metering pump is not pumping or the system is otherwise idle. As has been noted above, to allow liquid polymer to come into contact with water or an aqueous solution when such is not desired will activate the polymer and thus cause extensive coagulation of the polymer, which will thus foul and clog the components and piping of the apparatus.  
           [0005]    The present invention provides apparatus and a technique for blending and/or isolating two fluids. Although this technique has wide application to a number of mixing protocols, it is particularly useful for mixing liquid polymers and water to create solutions commonly used in water treatment and wastewater treatment processes.  
           [0006]    According to an aspect of the invention, when in use, water can be continuously directed into one end of a mixing assembly. In the central section of the mixing assembly, liquid polymer enters the water stream by the exertion of hydraulic pressure in the polymer supply line that overcomes the seal formed by a spring-loaded ball. The polymer supply line pressure, generated by a polymer feed pump, overcomes the force holding the ball in sealing engagement with a valve seat and forces the ball off the valve seat, thus allowing the polymer to flow between the valve seat and the ball in the shape of a thin, cone-shaped stream as it begins passing around the ball. The polymer will then disperse rapidly into the vigorously flowing water stream which is passing tangentially through the vicinity of the valve. This technique produces easy and instantaneous blending of the liquid polymer and water, allowing the thusly formed mixture to exit the mixing assembly as a “pre-blended solution.” 
           [0007]    The mixing assembly of the invention improves the overall polymer dilution process by providing a pre-blended solution of polymer and water, sufficient to avoid unwanted coagulation, before the mixture thus formed enters a downstream primary mixing or activation mechanism for more thorough mixing. The mixing assembly of the invention thus provides immediate “pre-blending” or “pre-mixing” of the two fluids as soon as they come into contact with each other. This immediate pre-mixing is important in applications where the fluids react with each other rapidly to produce highly viscous solutions.  
           [0008]    Equally important, during periods of time when the system is idle, the mixing assembly of the invention completely seals off one fluid from the other fluid, thus preventing any leakage and inadvertent contact that could result in coagulation and system clogging or fouling.  
           [0009]    In a typical system, a metering pump controls the amount and flow of polymer delivered to the mixing assembly and a water regulator or pump typically controls the flow of water into the mixing assembly, as measured, for example, by a rotameter or a flow meter. Thus, the desired ratio of polymer to water can be easily maintained by controlling the polymer metering pump and the water supply, either manually or automatically, in known ways.  
           [0010]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description, drawings and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a schematic representation of a mixing system according to the invention.  
         [0012]    [0012]FIG. 2 is a sectional elevation view of a mixing assembly according to the invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]    In the particular system of FIG. 1, water regulator or pump  10  supplies water from water source  22  at a constant, but adjustable rate. The water flows through rotameter or flow meter  12 , throttling valve  11  for flow control, and then into water inlet port  104  of mixing assembly  100 . The rotameter or flow meter  12  measures the water flow rate and the throttling valve  11  permits flow control of the water source  22  either manually or automatically, in ways known to those of ordinary skill in the art. Polymer metering pump  14  pumps, under pressure, a predetermined quantity of liquid polymer from liquid polymer source  16  to polymer inlet port  102  of mixing assembly  100 . The liquid polymer is injected with force into a turbulent water stream, thus forming a pre-blended solution of the fluids in mixing assembly  100 . This polymer/water mixture then moves toward mixture (or polymer solution) outlet port  106  from the vicinity of ball  108  (FIG. 2). Further mixing occurs here due to the flow turbulence of the water stream. The liquid polymer/water mixture exits mixing assembly  100  through mixture outlet port  106 . The mixture then flows into primary mixing device  20  downstream of mixing assembly  100  where thorough mixing and final polymer activation occurs.  
         [0014]    Referring to FIG. 2, water flows into mixing assembly  100  at water inlet port  104 . As shown, liquid polymer can enter the mixing assembly at the polymer inlet port  102  and around ball  108  when the device is in operation. When the device is not in operation, ball  108  mates with valve seat  112  as a result of at least the seating force imparted by spring  110 . Spring  110  is situated between ball  108  and recessed area  128  on the inside surface of injector housing  114 . Ball  108  provides a liquid tight seal against valve seat  112  when they are mated. Polymer metering pump  14  is designed to provide a polymer pressure great enough to overcome the force of spring  110 . This pressure forces ball  108  off valve seat  112 , thus allowing liquid polymer to flow around ball  108  and disperse into the flowing water passing by ball  108  in a fine, thin conical stream. This liquid polymer stream instantaneously blends with the water flowing past ball  108  toward mixture outlet port  106 . The mixture then exits the mixing assembly  100  through the mixture outlet port  106 .  
         [0015]    Valve-securing member  116  holds valve seat  112  in place. Securing hardware  118  attaches valve-securing member  116  to injector housing  114 . In the drawing, pipe-mating member  130  is integral with valve-securing member  116 . Pipe-mating member  130  has threads which co-act with threads on union  120  to allow easy connection of mixing assembly  100  to polymer supply line  134 . O-ring  126  is provided to prevent liquid polymer from leaking where polymer supply line  134  meets mixing assembly  100 . O-ring  124  is also provided to prevent leakage of liquid polymer between valve seat  112  and valve-securing member  116 . Another O-ring  122  is provided to prevent leakage of liquid polymer between injector housing  114  and valve seat  112 . Alternates to the O-rings and securing hardware  118  can, of course, be implemented in place of the specific features described above, as will be readily apparent to those of ordinary skill in the art.  
         [0016]    Mixing assembly  100  can generally, but need not, be configured as shown in FIG. 1 and FIG. 2, with the liquid polymer entering mixing assembly  100  from below. Such a configuration is desirable because gravity would then assist spring  110  with seating ball  108  on valve seat  112 . Other orientations or configurations can, of course, be used as alternatives without departing from the spirit and scope of the invention.  
         [0017]    In a typical system, polymer metering pump  14  is capable of producing a pressure ranging from approximately 50 to approximately 150 pounds per square inch and the ball  108  and spring  110  arrangement is designed to unseat at a liquid polymer pressure of approximately 30 pounds per square inch. This unseating pressure can be adjusted by using alternative pumps and/or springs having different physical and operational characteristics, as will be readily apparent to those of ordinary skill.  
         [0018]    Because certain liquid polymers have been found to be somewhat corrosive, spring  110  is made of various metallic materials and then coated with a protective material to enhance its ability to resist corrosion. Such protective materials can typically be plastic, rubber or other synthetic or synergistic type coatings. Ball  108  can be made of various metallic materials, ceramic, or synthetic materials. If made of stainless steel, ball  108  can be coated with a protective material to enhance its resistance to corrosion. Such protective materials can typically be plastic, rubber or other synthetic or synergistic type coatings. Valve seat  112  can be made of, or can comprise, a more pliable synthetic material than ball  108  comprises. The combination of a harder ball  108  with a softer, more pliable valve seat  112  provides an excellent seal for preventing inadvertent leakage of liquid polymer into the water stream, or vice versa. This excellent seal is achieved because a more pliable valve seat  112  can conform to ball  108 . Of course, as will be readily appreciated by one of ordinary skill, ball  108  can comprise the more pliable material, with valve seat  112  being made of a harder material to provide excellent sealing capability.  
         [0019]    Other parts of the mixing assembly  100  may be constructed using synthetic materials, such as acrylic, polycarbonate and polyvinylchloride (PVC), as well as stainless steel. Various components such as injector housing  114  and valve-securing member  116  may be made of transparent or translucent material, if desired, to allow visual observation of the operation of mixing assembly  100 .  
         [0020]    Mixing assembly  100  can be designed for handling a wide range of water flow rates typically from a fraction of a gallon per minute up to several hundred gallons per minute. Mixing assembly  100  can also be designed to handle a wide range of polymer flow rates ranging typically from a fraction of a gallon per hour, up to several hundred gallons per hour. In a typical system, a rotameter or flow meter  12  is used to measure the water flow rate and a metering pump  14  is used to set the liquid polymer flow rate. Adjusting these parameters sets the desired ratio of polymer to water. This can be done either manually or automatically, as will be readily apparent to one of ordinary skill. Useful solutions of liquid polymers in various water treatment or wastewater treatment processes can have concentrations, say, from approximately 0.25% polymer by weight or volume up to, say, approximately 10% polymer by weight or volume. As will be appreciated, these percentages can vary beyond the stated amounts.  
         [0021]    A number of embodiments and variations of the invention have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. For example, the techniques disclosed herein can be used to mix fluids other than those specifically disclosed herein. Additionally, other materials may be used to form the different components described herein. Accordingly, other embodiments are within the scope and spirit of the invention and the following claims.