Uniform small particle homogenizer and homogenizing process

Details Uniform small particle homogenizer and homogenizing process Uniform small particle homogenizer and homogenizing process

2002-09-30

2004-12-07

Soohoo, Tony G (Department: 1723)

Agitating

Having specified feed means

Impinging jets

C366S173200, C366S176400, C366S181800, C366S182200

Reexamination Certificate

active

06827479

ABSTRACT:

TECHNICAL FIELD
The invention pertains to homogenizers that generate high pressure in general, and more specifically to a homogenizer that utilizes at least two hydraulically driven cylinder pumps that alternately reciprocate to create a constant pressure and product flow rate.
BACKGROUND ART
Homogenization is a process by which, for the purpose of this invention, a fluid is made more uniform throughout in texture, mixture, quality, etc. by breaking down and blending the particles that comprise the fluid. It is often necessary to homogenize an emulsion, which is a system comprising two immiscible liquid phases, with one hydrophobic “oil” phase dispersed as small particles between 1 nm and 1000 nm in a second hydrophilic “water” phase. Emulsions have come into large-scale use in applications ranging from food and medicine, to industrial material and art supplies.
Previously, many types of homogenizer have been used in endeavoring to provide an effective means to form emulsions. However, the prior art listed below did not disclose any patents that possess the novelty of the instant invention, however the following U.S. patents are considered related:
U.S. Pat. No.
Inventor
Issue Date
4,533,254
Cook et al.
August 1985
4,952,067
Dallas
August 1990
5,116,536
Bucheler et al.
May 1992
5,720,551
Shechter
February 1998
5,749,650
Kinney et al.
May 1998
5,899,564
Kinney et al.
May 1999
6,085,664
Klinksiek
July 2000
6,238,080
Jarchau
May 2001
Other Publications
Microfluidics Industrial Pilot Scale Microfluidizer Processors M-700 Series Brochure.
Currently high pressure homogenizers are used to produce small, uniform particles by utilizing a homogenizing valve, orifice or chamber. There are a number of patents covering many types of homogenizing valves, orifices and chambers, each to describing how to obtain small sized particles, to raise efficiency and how to improve particle uniformity.
Cook et al. in U.S. Pat. No. 4,533,254 discloses a high pressure homogenizer with two or more fixed orifices used to run premixed raw emulsion forms into each other. The process is capable of reaching pressures of about 40,000 psi.
Dallas U.S. Pat. No. 4,952,067 discloses a device that comprises a stack of stainless steel disk valves, a design intended as an improvement to those detailed in U.S. Pat. Nos. 2,882,025 and 4,383,769. Dallas teaches this improvement on the older designs in manners of cleanliness while maintaining effectiveness in the creation of the emulsion.
Bucheler et al. in U.S. Pat. No. 5,116,536 discloses a process for the preparation of stable, fine particled dispersions from pre-emulsions prepared by known emulsifying methods. Under the Bucheler et al. process, the pre-emulsion is passed to a pressure release jet, which operates at technologically optimal conditions allowing the use of lower pressures and improving the economics of the known process.
Shechter in U.S. Pat. No. 5,720,551 discloses a method where a structure in the path of a jet of fluid controls the flow of one fluid component into a stagnant supply of a second fluid component to cause shear and cavitation in the fluid interface.
Kinney et al. in U.S. Pat. Nos. 5,749,650 and 5,899,564 discloses a homogenization valve designed to improve homogenization efficiency.
Klinksiek in U.S. Pat. No. 6,085,664 discloses a process for homogenizing milk with a high-pressure homogenizer that uses a small valve aperture to allow for higher throughput and/or volume flow with a lower pressure.
Jarchau in U.S. Pat. No. 6,238,080 discloses a homogenizing valve through which the fluid crosses from an outside high-pressure volume to a central low-pressure volume and an actuator controls the width of the gap with the transition homogenizing the fluid.
In addition to the types of homogenizing valves, orifices and chambers, the power sources that are used in the homogenization process also play an important role in acquiring small particle size and raising performance efficiency. Whether single pump or multi-pump systems, the previously disclosed technologies do not establish a flow overlap to maintain a constant pressure that yields a substantially uniform particle distribution. The uniformity provided by the inventive homogenizer greatly decreases the variation in particle size, which improve emulsion quality.
Some commercially available homogenizers provide at least two intensifier pumps, which may be operated with either independent product streams of the same product. The term “power stroke” is used to describe the motion of the pump, where the product is forced to go through an interaction chamber that moves from a high pressure to a low pressure, thus breaking down the “oil” phase into smaller droplets. The term “suction stroke” is used to describe the motion that introduces product into the intensifier pumps.
One example of the use of two intensifier pumps utilizes one motor to operate two independent hydraulic pumps and hydraulic systems, which include valves and cylinders etc. The hydraulic cylinders are directly connected to single-acting intensifier pumps that amplify the high hydraulic pressure to the cylinder to reach a higher product stream pressure in the intensifier pumps. At the beginning of the power stroke the product stream flow-rate increases form zero to a constant value. The flow-rate remains constant during most of the power stroke. At the end of the power stroke the product stream flow-rate decreases and finally becomes zero. At the zero flow rate, the intensifier pump reverses its direction and fresh product is drawn into the pump. At the end of the suction stroke the pump again reverses direction and a new power stroke begins. During the power stroke period the product is forced out of the pump. Each pump has its own interaction chamber in which the product accelerates to two high velocity streams that then collide with each other, thus creating shear and impact forces within the product stream, which brings about the immiscible emulsions.
The quality and stability of emulsions depend upon the average particle size and size distribution. An emulsion consists of two immiscible liquid phases consisting of one “oil” phase suspended within a second “water” phase. In an emulsion the oil phase particles or droplets strike each other due to Brownian motion or shaking. The particles will continue to strike each other and merge into particles of increasing size. The larger the particles are that collide, the larger the resulting particles will be when formed as a result of the merging process. The frequency of the collisions combined with the resulting larger particle sizes deteriorates the quality of the product.
One way to reduce the size of the oil particles is to let the product pass through the homogenizer several times, however this technique yields low efficiency during processing and the average size of the particles may become too small.
The particle size depends upon the shear and impact forces in the interaction chamber, however both the shear forces and impact forces depend on the product stream velocities which in turn depend on the flow-rate of the product stream. A low product stream flow-rate will create a minimal velocity which yields particles with large diameters. In this low-product stream flow rate, the power stroke will always contain ramp up (at the beginning) and ramp down (at the end) periods with slower flow-rates.
DISCLOSURE OF THE INVENTION
The invention discloses a homogenizer and a homogenization process that overlaps the end of one intensifier pump power stroke with the beginning of another intensifier pump power stroke. Both of the pumps are configured to share one interaction chamber since the flow of each pump enters a single interaction chamber and the power strokes are precisely arranged so that the homogenizer maintains a high pressure and a high product flow-rate throughout the pump cycles. Alternating the two pumps with appropriate timing will therefore reduce flow-rate variance, thus removing any decreases in flow-rate or product flow.
The primary object of the invention is described

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