Liquid purification or separation – With alarm – indicator – register – recorder – signal or...
Reexamination Certificate
2002-07-24
2004-07-06
Cecil, Terry K. (Department: 1723)
Liquid purification or separation
With alarm, indicator, register, recorder, signal or...
C210S096100, C210S299000, C210S511000, C137S173000, C422S256000, C073S061590, C073S863210
Reexamination Certificate
active
06758964
ABSTRACT:
DESCRIPTION
The invention relates to a device for separating phases of a diphasic mixture and the application of this device to the determination of the physical and/or chemical parameters of a diphasic mixture, in particular a liquid—liquid diphasic mixture, preferably a liquid—liquid diphasic emulsion.
In particular, the invention enables the physical parameters of a diphasic mixture, such as a diphasic emulsion, to be determined by propagation of plane sound waves.
Within the scope of the present invention, diphasic mixture is generally understood to mean any emulsion or dispersion in which a first phase, for example a solution, is in the form of a continuous phase, and a second phase, for example a solid, liquid or gas phase, is in the form, for example, of droplets or particles dispersed in the continuous phase. The second phase is usually called “dispersed phase”.
This type of diphasic mixture is used in particular to separate chemical elements in solution. The separation process essentially consists in bringing into contact a first solution, for example an aqueous solution, containing chemical elements, with a second solution comprising, for example, an organic solvent, which plays the role of an extractant. This bringing into contact is intended to allow a transfer of material between the two solutions.
The transfer of material is favoured by the formation of a diphasic mixture in the form of an emulsion or dispersion with fine droplets, in such a way as to increase the interfacial exchange area between the phases present. Decantation then allows the liquids to be separated after the transfer of the material.
Different separation devices that operate according to the process mentioned above are known. Among these, mixer decanter type devices, centrifuge extractor type devices or pulsed column type devices may be cited.
In extraction columns, two liquid phases are made to circulate in counter-current, wherein the heavy phase is injected into the top of the body and the light phase is injected into the bottom of this body. By bringing these two phases into contact, the element to be separated is shared out between each of the phases according to the laws of chemical thermodynamics and, by playing on the affinity of an element for one of the phases, one can extract this element almost completely and separate it from other elements.
Thus, in particular, liquid—liquid extraction processes, used in reprocessing of used fuel operations, are carried out in contactors that, in their mixing zone, produce diphasic emulsions. The efficiency of the transfer of elements between phases is particularly linked to the local volume percent of the dispersed phase and the local interfacial exchange area, but one also seeks to determine other physical and chemical parameters of liquid phases present in the emulsion zone, such as elementary concentrations of elements (for example U, Pu), conductivity, acidity, density, etc.
These various parameters may be determined by several procedures. The first procedure consists in taking a sample, in other words a small volume of emulsion, and carrying out measurements on each phase after leaving them to decant.
However, this type of procedure has disadvantages. In fact, taking a sample of emulsion disrupts the hydraulic operation of the contactor.
Moreover, sampling is only possible if the separation device contains a sufficient volume of mixture. Furthermore, the sampled volume must be re-injected into the separation device or must be stored after each measurement. In addition, in the event where the diphasic mixture contains very radioactive substances, the sampling and the storage of measurement samples may be impracticable or very restricting.
A second procedure, intended in particular to establish the density of the continuous phase and the velocities or propagation times of the waves separately in each of the phases during processing, consists in installing, in the separation device, decantation chambers, near to a mixing zone. These “in situ” decantation chambers are however likely to modify the hydraulic behaviour of the device and to locally modify the characteristics of the diphasic mixture.
More precisely, as regards more specifically the local retention rate, a method for measuring the local retention rate by ultrasound wave propagation has already been described in documents (1), (2) and (3).
It shows that this parameter &bgr; may be represented by:
β
=
t
-
t
c
g
d
t
d
-
g
c
t
c
(
1
)
wherein:
t, t
c
and t
d
=time of flight of the ultrasonic wave in the emulsion, the continuous phase and the dispersed phase alone; and
g
c
and g
d
=correction factor for the acoustic path in the aqueous and organic phases.
When transfer of material between the phases occurs, an on-line calibration of the propagation velocities in each of the phases must be carried out under the same physical and chemical conditions as in the measurement in the emulsion.
A destructive method has been proposed in document (4) by sampling and decanting a volume of emulsion before measurement.
An acoustic microscopy method has also been described in document (5) and has the advantage of being neither destructive nor intrusive, but it only allows one to determine the calibration parameter in the continuous phase.
Similarly, as regards the interfacial exchange area, there are optical methods for analysing the average size and the average number of droplets allowing the local interfacial exchange area to be determined. However, these techniques, by light diffusion and diffraction, assume that the local retention rate on-line is known; it is, for example, the principle on which are based the devices of the FORULACTION® Company, sold under the name TURBISCAN®.
The large amount of droplets does not allow simple determination, by analysis and image processing, to be conceived.
On-line determinations of other parameters are achieved through analyses on samples taken.
The measurement of the density of the continuous phase is achieved in document (5) by acoustic microscopy, but the method on its own does not allow the value in the dispersed phase to be determined.
The problem of determining the physical and chemical parameters is particularly acute in the devices presently used in new liquid—liquid extraction installations for the reprocessing of used nuclear fuels. In fact, in order to limit the volumes of nuclear material, the columns are very small.
In such devices, few samples may be taken on-line and the geometry of the extraction devices implies limiting, as much as possible, hydraulic disruptions by intrusion or local modification of the dimensions.
There is therefore a need for a device for separating and renewing the phases of a diphasic mixture, in particular a liquid—liquid diphasic mixture, for example a liquid—liquid diphasic emulsion, which does not modify the hydraulic behaviour of the device in which it is placed and which does not modify the characteristics of the diphasic mixture.
There is also a need for a device for separating and renewing the phases of a diphasic mixture, in particular a liquid—liquid diphasic mixture, which allows perfect, complete separation and renewal of the phases.
There is also a need for a device for measuring the physical and chemical parameters of a liquid—liquid diphasic emulsion, which allows these measurements to be made without taking samples, without intrusion, without inducing hydraulic disruptions and without modifying the characteristics of the diphasic mixture.
Finally, there is a need for a measurement device that allows such measurements to be made with a high degree of reliability and precision, whatever the nature and the volume of the emulsion.
The aim of the present invention is to provide a device for separating and renewing the phases of a diphasic mixture, for example a liquid—liquid diphasic emulsion, which meets, among others, the requirements cited above.
The aim of the present invention is also to provide a device for separating and renewing the phases of a diphasic mixture, for example
Malzieu Francis
Roudil Danielle
Cecil Terry K.
Commissariat a l'Energie Atomique
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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