FR2581452A1 - Method and system for measuring the frequency of pulsation of a pulsed medium - Google Patents

Abstract

Method and system for measuring the frequency of pulsation of a pulsed medium. From a signal correlated to this frequency Fo actually inside the medium, a processing of the signals in two parallel channels is effected: band pass filters 12.1, 12.2 with very close characteristics, circuits 13.1, 13.2, low-pass filters 14.1, 14.2, square-root extractors 15.1, 15.2; the difference in the output signals of these two channels is calculated and it is cancelled by varying the mean of the frequencies on which the response curves of the band pass filters are centred in order then to obtain the value of Fo. Application to the oil industry or to the reprocessing of irradiated fuels.

Description

Method and system for measuring the frequency of
pulsation of a pulsed medium
The subject of the present invention is a method for measuring the pulsation frequency of a pulsed medium as well as a system for implementing this method. It applies in particular to the measurement of the pulse frequency of a mixture of two liquid phases flowing against the current in a pulsed column of an installation.

 Said medium can be a fluid medium, that is to say a liquid or gaseous medium.

 Generally speaking, it is known that the pulsation of liquids inside apparatuses of the chemical industry is a conventional technique.

 In devices where a solid phase and a liquid phase are mixed, this pulsation causes the mixture to agitate allowing unclogging.

 In the devices where two liquid phases are mixed, which represents the case mainly concerned with the present invention, this pulsation causes agitation allowing in particular the transfer of solutes from one liquid to another. This solvent extraction technology is widely used in industry, especially for the reprocessing of irradiated nuclear fuels.

 This latter application is particularly important because of the development of the nuclear energy industry.

 However, the invention also relates to other fields such as those of the petroleum, pharmaceutical, Kydrometallurgical, chemical, etc. industries.

 Thus, the apparatus known under the name of "pulsed column", a column inside which circulate against the current two pulsed liquid phases, is it more and more frequently used.

 The object of the invention is to improve the operation of devices of this type and, more precisely still, of devices of this type comprising: a vertical barrel column, means respectively at the top and bottom of the column for introducing a first Liquid phase and a second liquid phase Inside the barrel, an electrically operated three-way pneumatic valve for pulsing the mixture of the two liquids flowing against the current inside the column, and means respectively at the bottom and at the top of the column for respectively withdrawing said second and first liquid phases after physical reaction of these two phases with one another.

 In apparatuses of the pulsed column type, it is very important to be able to control the characteristic parameters of the pulsation applied to the mixture of the two liquid phases, and in particular the frequency and the amplitude of the movement caused inside the barrel of the column by pulsation, to obtain a good agitation of the mixture without compromising its hydraulic functioning, and consequently an optimal efficiency of the desired physical reaction between the two phases.

 However, until now, in existing installations, only the frequency of the electrical control of the three-way valve is controlled, applying a pressure of compressed air which causes the hydraulic pulsation of the mixture; but this first control is insufficient to obtain a fairly precise subsequent control of this hydraulic pulsation inside the column itself due to dispersions or vagaries in the construction characteristics and / or operation of the pneumatic valves with electric control that are used.

 Consequently, the precise aim of the invention is to remedy this drawback by proposing a method and a system making it possible to measure the frequency of the hydraulic pulsation inside the same column, this measured frequency then allowing precise control of the operation of an installation which may include one or more pulsed columns.

 More generally, the invention relates to a method and a system making it possible to measure the frequency of pulsation of a pulsed medium even inside said medium.

 To this end, the invention firstly relates to a method relating to a pulsed medium.

et dont les courbes de réponses representant le gain en fonction de la fréquence sont sensiblement identiques,

étant très inférieur à Fc, à obtenir à partir de seconds signaux de sortie de ces deux filtres passe-bandes deux troisièmes signaux mesurant L'amplitude des seconds signaux, à obtenir une valeur de différence qui est nulle si et seulement si la différence de ces deux troisièmes s-ignaux L'est aussi, et à faire varier la valeur de la fréquence Fc jusqu'à ce que cette valeur d# différence soit nulle, la valeur de Fc étant alors La mesure cherchée de La fréquence de pulsation dudit milieu.The aim of this process is to measure the frequency of pulsation of the pulsed medium inside this medium itself. It is characterized in that it consists in obtaining a first measurement signal of a parameter in direct correlation with this frequency, to be processed. this first signal by two bandpass filters having transmitted frequency bands very close to each other, respectively centered on the values

and whose response curves representing the gain as a function of the frequency are substantially identical,

being much lower than Fc, to obtain from second output signals of these two bandpass filters two third signals measuring the amplitude of the second signals, to obtain a difference value which is zero if and only if the difference of these two third s-ignaux is also, and to vary the value of the frequency Fc until this value of difference is zero, the value of Fc then being the sought measure of the frequency of pulsation of said medium.

et dont Les courbes de réponses représentant le gain en fonction de la fréquence sont sensi blement identiques,

étant très inférieur à Fc, à obtenir à partir de seconds signaux de sortie de ces deux filtres passe-bandes deux troisièmes signaux mesurant L'amplitude des seconds signaux, à obtenir une va
Leur de différence qui est nulle si et seulement si la différence de ces deux troisièmes signaux L'est aussi, et à faire varier la valeur de La fréquence Fc jusqu'à ce que cette valeur de différence soit nulle, ta valeur de Fc étant alors La mesure cherchée de La fréquence de pulsation dudit mélange.The invention relates in particular to a method relating to an appliance of the "pulsed column" type comprising a vertical barrel column, means respectively at the top and at the bottom of the cotton to introduce a first liquid phase and a second liquid phase inside. of the barrel, an electrically operated three-way pneumatic valve for pulsing the mixture of the two liquids circulating against the current at
The very interior of the column and means respectively at the bottom and at the top of the column for respectively drawing off said second and first liquid phases after physical reaction of these two phases between them, this process having the purpose of measuring the frequency of pulsation of the mixture liquid inside the column and being characterized in that it consists in obtaining a first measurement signal of a parameter in direct correlation with this frequency, in processing this first signal by two bandpass filters having bands of transmitted frequencies very close to each other, respectively centered on the values

and whose response curves representing the gain as a function of the frequency are substantially identical,

being much lower than Fc, to obtain from second output signals of these two bandpass filters two third signals measuring the amplitude of the second signals, to obtain a va
Their difference which is zero if and only if the difference of these two third signals is also, and to vary the value of the frequency Fc until this difference value is zero, your value of Fc then being The desired measurement of the pulse frequency of said mixture.

 For the implementation of this method, the first measurement signal of a parameter will be obtained in direct correlation with the pulse frequency to be measured of the liquid mixture moving inside the column from either differential pressure measurements in two high and low points in the column, either of measurements of the level of the mixture varying with the pulsation, or of measurements of the weight of the column in pulsed movement, or of other measurements (concentrations, temperatures, densities, etc.), or even other sensors (nuclear meters, ultrasound, ...).

et dont les courbes de réponse représentant le gain en fonction de la fréquence sont sensiblement identiques,

étant tres inférieur à Fc, - des moyens pour obtenir à partir de seconds signaux
de sortie de ces filtres deux troisièmes signaux me
surant l'amplitude des seconds signaux, - des moyens pour obtenir une valeur de différence qui
est nulle si et seulement si la différence de ces
troisièmes signaux L'est aussi, - des moyens pour déterminer si cette valeur de diffé
rence est nulle ou non, et - des moyens pour faire varier la valeur de la fréquen
ce Fc jusqu'à ce que la valeur de différence soit
nulle, la vaLeur de Fc étant alors la mesure cherchée
de la fréquence de pulsation.A second object of the invention is a system for measuring the pulse frequency of a pulsed medium, characterized in that it comprises - means for obtaining a first measurement signal
a parameter directly correlated with this fre
quence inside the pulsed medium, - two bandpass filters intended to treat this pre
mier signal and having trans frequency bands
bets very close to each other, respectively "centered" on the values

and whose response curves representing the gain as a function of the frequency are substantially identical,

being very less than Fc, - means for obtaining from second signals
output of these filters two third signals me
monitoring the amplitude of the second signals, - means for obtaining a difference value which
is zero if and only if the difference of these
third signals Is also, - means to determine if this value of diff
frequency is zero or not, and - means to vary the value of the frequency
this Fc until the difference value is
zero, the value of Fc then being the measure sought
of the pulse frequency.

 The inventio # makes it possible in particular to carry out permanent control of an installation incorporating one or more devices of the "pulsed column" type.

 By "installation" is meant an extraction installation.

 More generally, the method and the system which are the subject of the invention can be used for all pulsed devices in the chemical industry, pulsed filters for example.

The following description, given for information only and in no way limiting, will allow a better understanding of the invention. It is made with reference to the accompanying drawings, in which:
FIG. 1 very schematically represents an installation with a pulsed column of the conventional type incorporating the improvements made by the present invention,
FIG. 2 gives the functional diagram of electronic circuits or of digital calculation algorithms making it possible to implement the method of
The invention,
FIG. 3 gives the response curves of two bandpass filters used in these circuits, and
- Figure 4 is the graph of the frequed; this pulsation measured by the method of the invention as a function of the frequency actually imposed by the pneumatic pulsation device.

 First of all, general explanations will be provided on the previously known methods for extracting a solute contained in a first liquid phase in immiscible contact with a second liquid phase inside an extraction column.

 During this contact, the solute is divided in each of the phases according to the Laws of Thermodynamics (equality of chemical potentials at equilibrium).

 By playing on Affinity. of a solute, in a mixture, for a phase, one can manage to extract it almost completely and to separate it from the others.

In general, this affinity is relative, and a partition coefficient D is defined, such that:

C1 being the concentration in phase 1, and C2 being the concentration in phase 2.

 In the general case, before the first contact, we have C1 = 0 in the extracting phase and C2 = C in the phase to be extracted.

The concentrations, after a contact of two equal volumes, are given by the following relationships
C1 + C2 = C
C1 = duc2 either
After n contacts,

Depletion is therefore all the more rapid the greater the partition coefficient D.

 The extraction devices are designed to ensure the equivalent of several contacts, without these necessarily being materialized.

 These devices use extraction columns in which the two liquids flow against the current, the heavy phase being injected at the top of the column and the light phase at the bottom.

 The operator chooses the phase he wants to continue and fills in the column.

 The other physis is then introduced and disperses in the first.

We define an important parameter called retention rate ss; if VD is the volume of dispersed phase contained in a volume V of the column, p is calculated by means of the following relation: V
D
= 100 (in percentage)
This parameter is extremely important insofar as it conditions the operation of the columns: - if it is too low, the drops will pass easily
in the column, but the material flow ex
milking will be small, and - if it is too strong, the efficiency will be greater
but we can reach a local coatescence too
significant drops leading to an inversion of
phases and engorgement of the column.

 The correct operating zone is therefore placed between these two extreme situations, the approach of which can be appreciated by measuring the retention rate. Unfortunately, this measure does not exist; only The value of the operating parameters is accessible.

 The value of this rate depends on many factors: # hysico-chemical, operative, etc ...

 The most important of these factors is certainly the energy which is supplied to the two-phase device to maintain the dispersion; several devices currently exist, mechanical or pneumatic.

 For safety reasons, the pneumatic device by pulsating leg tends to generalize today: this is the system adopted to equip your columns in factories for reprocessing irradiated nuclear fuels. The intensity of the pulsation therefore appears as an operating parameter that must be precisely controlled.

 Figure 1, to which we will now refer, very schematically shows a pulsed column 1 with a vertical shaft.

 The liquid organic solvent is introduced via an inlet 3 situated at the lower part of the barrel of the column and leaves via an outlet 4 situated at the upper part of this barrel.

 The aqueous phase, containing the material to be extracted in the case of an extraction operation, is introduced via an inlet 5 located at the top of the column barrel and withdrawn through the outlet 6 located at the bottom of this barrel.

 The apparatus shown in Figure 1 operates in the continuous aqueous phase. The solvent is dispersed in the form of drops which coalesce in the upper part called "decanter". The separation surface between the solvent and the aqueous phase in the decanter is called "interphase". The position of the interphase in the decanter is called "interphase level".

 The measurement of the level of the interphase, which can provide the first signal necessary for the application of the method of the invention, is carried out in the decanter in a known manner, by continuous measurement, and makes it possible to control the withdrawal rate of the liquid. , at the bottom of the column as illustrated by the functional block s and the two arrows in dashed lines connecting this block respectively to the interphase levels and to the withdrawal device d connected to the pipe 6.

 The two liquid phases, namely the light phase of the solvent introduced via inlet 3, and the heavy phase of the solute introduced through inlet 5, therefore flow vertically inside the barrel 2 of column 1 .

 Their mixture is pulsed inside this barrel thanks to the action of a pulsating leg J.

 This leg comprises a source of compressed air 7 connected by a pipe to one 8.1 of the channels of a three-way valve 8. Another channel 8.2 is connected to the open air and the third channel 8.3 is connected to a pipe 9- also connected to the lower part of the barrel 2 of column 1 below the inlet 3 of the organic solvent.

 The valve 8 is controlled by an electrical control device, shown diagrammatically by the functional block 11, to alternately place the interior of the pipeline 9 (channel 8.3) in communication with the compressed air source 7 (channel 8.1) and L respectively. air (track 8.2).

 The Liquid contained in the line 9 is thus pushed alternately by the compressed air (as shown by the opposite arrows 10) and is therefore driven back and forth which is communicated inside the column. This causes a pulsation of the emulsion with an amplitude which depends on the pressure drop of the various pipes connected at the bottom of the column (withdrawal of the aqueous phase, solvent inlet, bubbling of any differential pressure measurements).

 The operation of these pulsed columns, which requires a correct adjustment of the retention rates, requires a precise knowledge of the pulsation conditions and, in particular, of the frequency. Since the electrical control 11 cannot take account of any faults, irregularities and / or failures of the pulsation valves 8, only an in-situ measurement will guarantee operation. It is precisely the object of the invention to provide for this by proposing to carry out a measurement of the pulsation frequency Fo inside the column itself.

 This measurement is carried out by processing a signal, for example of differential pressure, representing the instantaneous "weight" of the column and which takes into account the pulse pressure wave.

 In principle, the method of the invention therefore consists in processing this signal s, for example delivered by the circuit s, by an adequate information processing circuit, the diagram of which is given in FIG. 2.

étant très inférieur à Fc, et dont les courbes de réponse en fréquence sont données à la figure 3 sur laquelle on a porté en abscisses La fréquence F (exprimée en Hz) et en ordonnées le gain G, la fréquence Fc étant égale à 1 Hz sur cette figure 3.This circuit includes two bandpass filters 12.1 and 12.2 whose transmitted frequency bands are very close to each other and respectively "centered" on the values

being much lower than Fc, and whose frequency response curves are given in Figure 3 on which we plotted on the abscissa The frequency F (expressed in Hz) and on the ordinate the gain G, the frequency Fc being equal to 1 Hz in this figure 3.

pour l'une des courbes et à

pour t'autre, d'où l'em- ploi de l'expression "centrées".We see in Figure 3 that these curves each have a "peak" corresponding to the value

for one of the curves and at

for the other, hence the use of the expression "centered".

définit la bande de fréquence de l'un des filtres et que

définit la bande de fréquence de l'autre filtre.We can also say that

sets the frequency band of one of the filters and that

sets the frequency band of the other filter.

 These two filters will give an identical result only if the pulse frequency Fo is located at the intersection of the two response curves.

alors S sera nulle lorsque Fc sera égale à la fréquence de pulsation.If we note A.G1 and A.G2 the amplitudes of the signals obtained after filtering by these two filters of the signal s of amplitude A, and S the expression:

then S will be zero when Fc is equal to the pulse frequency.

The values of A. G1 and A.G2 are obtained by raising the value of the output channels Y1 and Y2 of the two bandpass filters 12.1 and 12.2 squared by the corresponding circuits 13.1- and 13.2 which respectively deliver the signals Z1 and Z2. The signals Z1 and Z2 are respectively processed by two low-pass filters 14.1 and 14.2 which generate signals U1 and U2 respectively. Circuits 15.1 and 15.2 then calculate the square root of the value of the signals U1 and U2 respectively and output signals of respective values A.G1 and A.G2.A circuit 16 calculates the expression:

A logic circuit 17 determines whether the expression S is non-zero or zero. If it is not zero, this circuit 17 controls by its output 18 a circuit 19 modifying the value of the frequency Fc and the processing cycle resumes. If the expression S has a zero value, the value of Fc then displayed in a circuit 20 is the measurement of the pulse frequency Fo in the column
The example used, described below, relates to the measurement of the pulsation frequency of a column equipping a plant for the reprocessing of irradiated nuclear fuels.

 The difference in pressures taken from each end of the column barrel is analyzed by a differential pressure transmitter Le and treated as described above.

To demonstrate the validity of the process, the actual pulse frequency Fr expressed in Hz (FIG. 4) was varied from 30 strokes per minute tcps.mn), or 0.5 Hz, to 100 strokes per minute, or 1.666 Hz. We have plotted on the abscissa on the graph of FIG. 4,
The frequency Fm measured by the method described and expressed in Hz, as a function of the actual frequency Fr imposed by the pulsation system and plotted on the ordinate.

 The following table, on which the numerical values of the graph in FIG. 4 are plotted, shows that the relative error remains less than 0.3X.

(asservissement à actions proportionnelle, intégrale et dérivée).BOARD
FREQUENCY FREQUENCY ERROR
IMPOSED RELATIVE MEASURE
(cps.mn-l) (cps.mn 1)
30.00 30.06 0.20 X
35.30 35.33 0.08 X
40.00 40.06 0.15 X
46.15 46.24 0.2 X
50.00 50.12 0.24 X
54.54 54.69 0.28 Z
60.00 60.15 0.25 X
66.67 66.84 0.25 X
75.00 75.19 0.25 X
85.71 85.90 0.22 X
100 100.03 0.03 X
The circuit modifying the value of the cutoff frequency Fc, circuit referenced 19 in FIG. 2, can be produced by the use of control methods well known in the field of automation, and such as

(proportional, integral and derivative action slaving).

 There is shown diagrammatically in FIG. 1, by the functional block 21, all of the circuits of FIG. 2 and, by the functional block 22, connects to the block 21, circuits making it possible to inform the operating personnel of the pulsed column, the actual pulse frequency Fo, and warn it of any faults by comparing Fo to a set value.

Claims (4)

 1. Method for measuring the frequency of pulsation of a pulsed medium, characterized in that it consists, in order to measure the frequency of pulsation (Fo) of the medium inside this CeLui thereof, to obtain a first signal (s) for measuring a parameter directly correlated with this frequency (Fo), to process this first signal by two bandpass filters (12.1, 12.2) having transmitted frequency bands very close to one of L 'other, respectively' centered 'on values

 and whose response curves representing the gain as a function of the frequency are substantially identical,

 being very inferior to Fc, to obtain from second output signals of these two bandpass filters two third signals (A.G1, A.G2) measuring the amplitude of the second signals, to obtain a difference value which is zero if and only if the difference of these two third signals is also, and to vary the value of the frequency Fc until this difference value is zero, the value of Fc then being the sought measure of the frequency of pulsation (Fo) of said medium.  2. Method according to claim 1, characterized in that the pulsed medium is a mixture of two liquid phases flowing against the current in a pulsed column of an installation, said pulsed column comprising: a column (1) with vertical barrel ( 2) means respectively at the top (5) and column column (3) for introducing a first liquid phase and a second liquid phase inside the barrel, a three-way pneumatic valve (8) (8.1, 8.2, 8.3 ) electrically controlled (11) to pulsate the mixture of the two liquids circulating against the current inside I1 nee nee of the column, and means respectively at the bottom (6) and at the top (4) of the column for withdrawing respectively said second and first liquid phases after physical reaction of these two phases with each other, the pulsation frequency (Fo) of the liquid mixture being measured inside the column.  3. System for measuring the pulsation frequency (Fo) of a pulsed medium, characterized in that it comprises: - means (s) for obtaining a first signal of me  sure of a parameter directly correlated with this  frequency inside the pulsed medium, --two bandpass filters (12.1, 12.2) intended to  process this first signal and having bands of fre  transmitted quences very close to each other, respectively "centered" on Values

 and

 and whose response curves representing the gain as a function of the frequency are substantially identical,

 being much lower than Fc, means (13.1, 14.1, 15.1;  13.2, 14.2, 15.2) for  get from second output signals from these  filters two third signals measuring the amplitude  second signals, means (16) for obtaining a difference value  which is zero if and only if the difference of these  third signals is also, means (17) for determining whether this value of  difference is zero or not, and means (19) for varying the value of the  frequency Fc until the difference value  be zero, the value of Fc then being the measure  of the pulse frequency (Fo).