Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2001-01-24
2003-05-06
Bui, Bryan (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S103000, C073S584000
Reexamination Certificate
active
06560548
ABSTRACT:
TECHNICAL FIELD
This invention relates to a device and a process for determining the physical parameters of a two-phase mix by propagating an acoustic wave in the continuous phase of the mix. For example, the invention can be used to determine the propagation time of an acoustic wave in the continuous phase of the two-phase mix. In particular, the device can be used to measure the acoustic impedance of this phase, its density and the propagation velocity of the acoustic wave in the continuous phase.
For the purposes of the invention, a two-phase mix means any emulsion or dispersion in which a first solution or first phase is in the form of a continuous phase, and a second solid, liquid or gaseous phase is in the form of droplets or particles dispersed in the continuous phase. The second phase is called the dispersed phase.
This type of two-phase mix is used particularly to separate chemical elements in solution. The separation process consists essentially of putting a first solution containing chemical elements into contact with a second solution that acts as an extractor. Putting them into contact in this way enables transfer of material between the two solutions.
The transfer of material is facilitated by the formation of a two-phase mix in the form of an emulsion or dispersion of fine droplets. Settlement finally separates the liquids after the material has been transferred.
Different separation devices operating according to the process mentioned above are known. These include mixer-decanter type devices, centrifugal extractor devices, or pulsed column devices.
The invention may be used to analyze the physical or chemical properties of a two-phase mix, and in particular is used for monitoring parameters essential for such an analysis, namely firstly the propagation velocity of an acoustic wave in the continuous phase of the mix and secondly its density. A change in the propagation velocity is recorded whenever the density of the continuous phase is modified. For example, this type of change in the density corresponds to a transfer of material between the phases.
The invention is used for applications in the oil, pharmaceutical, chemical and food processing industries, in the treatment of radioactive waste and more generally in any field in which an emulsion needs to be characterized.
STATE OF PRIOR ART
When a separation process is used, the two-phase mix is usually monitored, particularly by determining the proportion of each phase in the mix.
Document (1), referenced at the end of the description, describes in particular a process for measurement of the fraction by volume of one of the phases in a two-phase mix consisting of a first phase F
1
kept inside a receptacle, in the dispersed state in a second phase F
2
. According to this process, the propagation velocity v
1
of an ultrasound signal in phase F
1
, and the propagation velocity v
2
of an ultrasound signal in phase F
2
are determined, and an ultrasound signal is then emitted at a point P
1
in the said receptacle, the passage of the said signal at a point P
2
in the said receptacle located at distance d from point P
1
is detected, the time t spent by the said signal to travel the distance d is determined, and the fraction by volume &egr;
1
of phase F
1
and/or the fraction by volume &egr;
2
of phase F
2
are calculated using the following equations:
ϵ
1
=
v
1
ⅆ
·
v
2
t
-
ⅆ
v
2
-
v
1
and
ϵ
2
=
v
2
ⅆ
·
v
1
t
-
ⅆ
v
1
-
v
2
Document (2), also referenced at the end of this description, relates to a similar process also using a method for measuring the propagation time for an acoustic wave in a two-phase mix.
The first step in calculating the fraction by volume of either of the phases, is to determine the propagation velocities (v
1
, v
2
) of the acoustic wave in each phase, as is the case in document (1).
Thus, document (2) describes how to measure the wave propagation velocity in each of the liquids to be mixed, before making the mix.
One difficulty in measuring the fraction by volume of either of the phases is due to the fact that the propagation velocities or propagation times are not constant during the separation. These parameters are influenced by temperature modifications, but also by changes to the density of the phases related to the material transfer.
It is not very difficult to determine the change in propagation velocities and times as a function of the temperature.
There are two possible methods at the moment of allowing for the change in propagation velocities or times as a function of material exchanges from one phase to the other.
The first method is to take samples of a small volume of emulsion during the separation treatment, and to make acoustic propagation velocity or time measurements separately in each phase after allowing them to settle.
However, there are disadvantages with this first method. Taking the sample of emulsion can disturb operation of the separation device. Furthermore, sampling is only possible if the separation device contains a sufficiently large volume of the mix. Moreover, the sampled volume must be reinjected into the separation device or must be stored after each measurement.
Finally, in the case in which the two-phase mix contains strongly radioactive bodies, it may be impossible to extract and store measurement samples.
A second method of determining the wave propagation velocities or times in each of the phases separately during the treatment is to form settlement chambers in the separation device adjacent to a mixing area. These “in situ” settlement chambers can modify the hydraulic behavior of the device and make local modifications to the characteristics of the two-phase mix.
These devices are also used for on-line measurement of the density of the continuous phase.
DISCLOSURE OF THE INVENTION
The purpose of this invention is to propose a process and a device for determining physical parameters such as the propagation velocity of an acoustic wave in the continuous phase of a two-phase mix, the acoustic impedance of the continuous phase and/or its density, and with none of the difficulties mentioned above.
One purpose in particular is to enable this type of continuous measurements to be taken without interrupting the separation process and without taking any samples of the two-phase mix.
Another purpose is to propose a non-intrusive device and process that have no influence on the hydraulic operation of separation equipment and that do not modify the characteristics of the two-phase mix.
In order to achieve these purposes, the purpose of the invention is more precisely a device for measuring the propagation time of an acoustic wave in a continuous phase of a two phase mix, the device comprising an electro-acoustic transducer capable of emitting acoustic waves and outputting a reflected acoustic wave reception signal, and means of using transducer signals to determine the time necessary for propagation of waves from the signals output by the transducer. The device also comprises means of focusing the acoustic waves in a focusing area and the frequency of the acoustic waves is adjusted to reflect the waves on the droplets of the dispersed phase, located approximately in the focusing area.
The wavelength &lgr; of the acoustic wave produced by the electro-acoustic transducer is such that:
λ
=
v
c
f
In this equation, V
c
represents the wave propagation velocity in the continuous phase and f is the wave frequency.
A droplet of the dispersed phase located within the focusing area causes a local disturbance of the acoustic impedance of the medium through which the wave passes at this location. The acoustic impedance of a medium is defined in this case as the product of its density and the wave propagation velocity in the medium.
The acoustic wave may be reflected by a droplet of the dispersed phase present in the focusing area and the energy of the reflected acoustic signal is proportional to the difference between the acoustic impedances of the dispersed phase and the continuous p
Attal Jacques
Combette Philippe
Despaux Gilles
Malzieu Francis
Roudil Danièle
Bui Bryan
Commissariat A l'Energie Atomique
Krebs Robert E.
Thelen Reid & Priest
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