Agitating – Having interrelated feed and discharge means – Recirculating from and to mixing chamber
Reexamination Certificate
2000-01-06
2001-09-18
Cooley, Charles E. (Department: 1723)
Agitating
Having interrelated feed and discharge means
Recirculating from and to mixing chamber
C366S152400, C366S160200
Reexamination Certificate
active
06290384
ABSTRACT:
BACKGROUND
The present invention relates to a method and apparatus for producing a liquid mixture having a pre-determined concentration of a specified component. More particularly, the present invention relates to such a method and apparatus in which component streams are mixed together to form an intermediate mixture having a lower concentration of the specified component than that desired for the mixture and a stream containing the specified component is added to such intermediate mixture so that the resultant stream has a pre-determined concentration of the specified component. Even more particularly, the present invention relates to such a method and apparatus in which part of the two component mixture is recycled to increase the homogeneity of the product.
There are many industrial processes that utilize liquid mixtures in which the concentration of the components of the mixture is particularly critical for the successful performance of the process. For example, in the manufacture of semiconductors, it is necessary that between processing steps, the wafer being processed be cleaned with an aqueous ammonia water solution.
The problem with producing such a solution with repeatable accuracy is that often the components are retrieved from bulk sources in which the components are mixed with other agents. As a result, the concentration of the components does not remain constant. For instance, in forming the aqueous ammonia solution, the ammonia component is drawn from a bulk source in the form of ammoniated water. Over time, however, the ammonia concentration within the water decreases due to the vapor pressure of the ammonia.
As will be discussed the present invention provides a method and apparatus for producing a liquid mixture with a reliably consistent concentration of the desired component.
SUMMARY OF THE INVENTION
In one aspect, the present provides a method of producing a liquid mixture having a pre-determined concentration of the specified component. In this regard, the term “mixture” as used herein and in the claims means either a suspension or a true solution. In accordance with the method, component streams are mixed together to form a first intermediate mixture stream having a lower concentration of the specified component than the pre-determined concentration. A stream containing the specified component is introduced into the first intermediate mixture stream to form a second intermediate mixture stream. The second intermediate mixture stream is then blended to produce a third intermediate mixture stream. The concentration of the third intermediate mixture stream is measured and the introduction of the stream containing the specified component is metered so that the intermediate mixture stream contains the specified component in the pre-determined concentration. A recycle stream, composed of the liquid mixture, is introduced into the intermediate stream to form a liquid mixture stream of the liquid mixture. The liquid mixture stream is divided into the recycle stream and a product stream.
In another aspect, the present invention provides an apparatus for producing a liquid mixture having a pre-determined concentration of a specified component.
The apparatus consists of a fluidic network having two inlet branches to mix component streams to form a first intermediate mixture stream having a lower concentration than the specified component of the pre-determined concentration. An intermediate branch is provided having an inlet to introduce a stream of the first component into the first intermediate mixture stream to form a second intermediate mixture stream. A means for blending the second intermediate mixture stream of the liquid mixture stream is provided to produce a third intermediate mixture. A recycle loop is also provided. The recycle loop has an inlet junction connected to the intermediate branch and an outlet junction to discharge a product stream composed of part of the liquid mixture stream. The recycle loop communicates between the outlet junction and the inlet junction, thereby to introduce a recycle stream composed of the remaining part liquid mixture into the third intermediate mixture stream to form a liquid mixture stream of the liquid mixture and to divide the liquid mixture stream into the recycle stream and a product stream. Also provided is a means for measuring the concentration of the intermediate mixture and a means for metering the introduction of the stream containing the specified component so that the first intermediate mixture stream contains the specified component in the pre-determined concentration.
As can be appreciated, since the first intermediate product stream has a lower concentration then that desired in the final mixture and the concentration is brought up in the first intermediate stream to form a second intermediate stream, the concentration of the specified component can be very accurately controlled. Since after the second intermediate stream is blended to form the third intermediate stream, the concentration is measured and used in metering the specified component, the product concentration can therefore be reliably adjusted. In order to further enhance the homogeneity of the mixture, that is to assure that there are no substantial temporal variations in concentration, the recycle loop or recycle stream can be provided so that part of the product is continually recycled into the third intermediate product stream. As a result, the variations in product concentration are very much reduced over prior art methods.
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Jansen Frank
Pozniak Peter M.
Roberts Benjamin R.
Cohen Joshua L.
Cooley Charles E.
Pace Salvatore P.
The BOC Group Inc.
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