FR2485941A1 - ANNULAR PULSED COLUMN - Google Patents

Abstract

THE SUBJECT OF THE INVENTION IS A PULSED ANNULAR COLUMN, USABLE IN PARTICULAR FOR THE TREATMENT OF IRRADIATED FUELS. THIS COLUMN CONSISTS OF AN EXTERNAL CYLINDRICAL ENVELOPE 1 OF VERTICAL AXIS IN WHICH IS AVAILABLE A CYLINDRICAL CORE 3 DELIMING INSIDE THE SAID COLUMN WITH THE EXTERNAL ENVELOPE 1 AN UPPER PART OF AN ANNULAR SECTION I EQUIPPED WITH INTRODUCTION MEANS 5 OF ' A HEAVY PHASE AND EVACUATION MEANS 7 OF A LIGHT PHASE, A CENTRAL PART II OF AN ANNULAR SECTION PROVIDED WITH A PADDING CONSTITUTED BY ANNULAR CHICANES 21-23 FOR THE CONTACTING CONTACT OF THE SAID PHASES, AND A LOWER PART III OF ANNULAR SECTION EQUIPPED WITH MEANS OF INTRODUCTION 13, 13 FOR THE LIGHT PHASE, WITH MEANS OF EVACUATION 15, 15 FOR THE HEAVY PHASE AND WITH MEANS 11 FOR GENERATING PULSATIONS IN THE MIXTURE OF THE SAID PHASES.

Description

The subject of the present invention is an annular pulsed column for the

  counter-current contacting two phases consisting of two immiscible liquids, a liquid and a gas or a liquid and a solid in the divided state.

  The pulsed columns currently known to

  generally, an upper part provided with a heavy phase inlet and a light phase outlet, a cylindrical central part having a vertical axis, provided with a packing consisting for example of perforated trays, a lower part comprising an inlet light phase and a

  heavy phase output, and a pulsation system permitting

  so much to engender a back-and-forth movement of the whole

  phases present in the column.

  The pulsation system generally used

  consists of a vertical tubing external to the colon

  partially filled by the continuous phase, the end

  lower part of this tubing leading to the lower part

  of the column and the upper end of this pipe being in communication with a source of compressed air capable of applying a periodic pressure as a function of time on the surface of the continuous phase present in the tubing so as to generate a movement back-and-forth of all the phases present in the

column.

  Columns of the above-mentioned type find many

  its applications, particularly in the nuclear field, where they are frequently used for the treatment of

  fuel solutions irradiated by soil extraction

  solvents. In this application, the risk of occurrence of a nuclear chain reaction in the liquids present in the column imposes certain limitations, in particular as regards the dimensions of the column, and the

  plutonium concentrations of the treated solutions.

  To avoid this drawback, it has already been envisaged the use of annular columns which, because of their particular geometry, can improve the processing capacity while respecting the imperatives of

nuclear surety.

  However, the annular columns known today

  The conventional packing comprising perforated trays does not provide a separation efficiency comparable to conventional cylindrical columns having the same cross section. The present invention specifically relates to an annular pulsed column which has the particular advantage of leading to obtaining a separation efficiency also

  good than that of conventional cylindrical columns.

  According to the invention, the annular pulsed column for the counter-current contacting of two phases, at least one of which is a liquid phase, comprises an outer cylindrical envelope of vertical axis in which is arranged coaxially a cylindrical core which defines inside said column with said envelope, an annular section upper portion provided with means for introducing a heavy phase and means for evacuating a light phase, a central portion of annular section provided with a packing for the countercurrent contacting of said phases, and a lower portion of annular section provided with

  means of introducing the light phase, means of evaluation

  cuation of the heavy phase and means to generate

  pulsations in the mixture of said phases, and it is

  characterized in that said packing consists of annular plates arranged horizontally and spaced apart from each other.

  other in the vertical direction, each of those trays does not

  that part of the cross-section of

  central part, said trays being divided into a first

  a series of trays in contact at their periphery with the central cylindrical core and in a second series of trays in contact at their periphery with the outer casing of

  said column, the trays of the first series being

  wedged between the trays of the second series.

  According to the invention, when the column is intended for the treatment of radioactive solutions, the central cylindrical core advantageously comprises an absorbent material or

slowing the neutrons.

  For example, the central core can be

  consisting of a container filled with a solution of

  absorbing or slowing neutrons such as cadmium, boron, gadolinium, or consist at least in part of a solid material absorbing or slowing neutrons such as polyethylene, carbon, boron concrete, boron carbide, boron, cadmium, hafnium

or boron steel.

  Preferably, the central core comprises a

  stack of cylindrical bodies in neutron concrete.

  According to the invention, the means for generating pulsations in the column advantageously comprise a pipe opening laterally into the lower part.

of the column.

  The annular pulsed column as characterized by

  The above-mentioned advantages in particular.

  Its annular shape and the presence of a neutron-absorbing nucleus makes it possible to obtain, with a suitable ring width, a column of section, and therefore of high capacity, which is safe from the point of view of nuclear criticality, and therefore extremely interesting for reprocessing plants for spent fuel;

  - the use of a lining consisting of annular trays

  baffle forming is particularly suitable for

  the annular geometry because it makes it possible to

  continuous side-stream flow of the column while regulating the field of fluid velocities, which provides efficiency and performance comparable to conventional cylindrical columns; and

  - generating pulsations in the column by.

  the intermediary of a-tubulure opening laterally and normally to the outer casing ensures proper operation, while lai-ssant free! fndi of the column for the support of the cylindrical core neutrophage material; As a result of this lateral positioning of the pulsation tubing, the lower part of the column may have an enlarged zone capable of constituting a de-entrainment zone or a settling-coalescing zone of the heavy phase before it exits.

of the column.

  Other advantages and characteristics of the

  will appear better on reading the description

  which follows doinne for illustrative and non-limiting purposes,

  referring to the single appended figure which represents schemati-

  only in vertical section an annular pulsed column,

selol 1 inven-tion.

  In this figure, it can be seen that the annular column comprises a cylindrical outer casing 1 of vertical axis in which is disposed coaxially a cylindrical core Z delimiting inside the column with the outer casing 1 an upper part I of annular section. , a central portion II of annular section, and a portion

  lower section III annular.

  In the upper part of the column, we introduce

  Dries the heavy phase by two pipes 5 diamtralerent opnosges

  and the light phase is evacuated by two diametrical lines

  opposite, which are equipped with vents 9 and which open

  in the column at a higher level than the pipes 5.

  At its lower part, the column is connected

  to a system for generating pulsations through

  mediate a single manifold 11 which opens laterally into the lower part III of the column, normally to

the outer envelope 1.

  This pipe 11 is connected by a part

  vertically ilb means for generating pulses

  on the surface of the continuous phase present in this tubing, these means may be constituted by a source of compressed air susceptible. to apply a periodic pressure as a function of time so as to generate a

  movement of the phases present in the colon-

  born. At the bottom of the column, the light phase is introduced, either by two diametrically opposed pipes 13 which open into the lower part III of the column, at a level higher than that of the pipe 11, or, in the case where it operates in the continuous light phase, through a pipe 13 'opening into the pipe 11. The heavy phase is discharged from the lower part of the column by two diametrically opposed pipes 15 which open into the lower part III of the column, to its lower end. However, in some cases, the heavy phase can be evacuated by a single pipe 15 'which opens into the lower part III, in particular when operating

at low rates.

  In the embodiment illustrated in this figure, the central core 3 comprises a container 3a in which is disposed a stack of cylindrical bodies 3b

in neutron concrete.

  Furthermore, the central core 3 and the outer shell 1 are flared at their upper and lower ends so that the upper part I and the

  lower part III of the annular column have

  the shape of a tulip and thus have an area with a

  However, the width of the annular zone is substantially the same as that of the central portion to maintain the nuclear safety characteristics. Thus, we create

  ends of the column of areas favorable to the

  or settling-coalescence of the heavy phase

  or the light phase, before leaving the column.

  However, it is specified that in certain cases, it is not necessary to provide a zone of greater section at the lower end of the column, in particular

  when the heavy phase is withdrawn via line 15 '.

  In its central portion II, the column comprises a packing constituted by annular plates 21 and 23 arranged horizontally and spaced from each other in the vertical direction. The plates 21 and 23 which each have the shape of a crown occupy only part of the cross section of the central portion II of the column, and these plates are distributed in a first series of plates 21 in contact by their periphery with the outer casing 1 of the column and in a second series of trays 23 in contact by their periphery with the outer wall 3a of the cylindrical core 3, the trays 21 of the first series being interposed between the trays 23 of the second series to form annular baffles in the path of fluids flowing in the column. In this part

  the column may be equipped with more than two

  the diametrically opposite intermediaries of introduction

of the light phase.

  It is specified that according to the invention the spacing between two adjacent trays 21 and 23 is chosen according to the invention.

  of the nature of the phase that constitutes the continuous phase.

  By way of example, when this continuous phase is constituted by the heavy phase, for example by an aqueous phase, good results are obtained with a spacing of approximately 40 mm. When the continuous phase is the light phase, for example an organic phase , good results

  are obtained with a spacing of about 20 mm.

  The annular column according to the invention can function

  using as a continuous phase, either the heavy phase or the

of, or the light phase.

  When operating in a continuous heavy phase, the light phase is introduced through the two lines 13 and the heavy phase through the two lines 5. After circulation in the column, the light phase is evacuated via the lines 7, in this case the upper part I plays the role of settling zone-coalescence for the light phase. The heavy phase is withdrawn from the column at a controlled rate, through the two lines 15 after having traveled the lower part III which plays, in this case, the role of de-entrainment zone.

for the heavy phase.

  However, when operating with a low flow rate, the heavy phase can be withdrawn via the pipe 15 ', the lower part of the column not having this phase.

  an enlarged form with a larger section area

  you. When operating in the continuous light phase, the heavy phase is introduced via the lines 5 and the light phase is introduced either by the lines 13 or by

  the pipe 13 'opening into the tubing 1i pulsations.

  After passing through the central part of the column, the heavy phase is drawn off at a rate regulated by the lines 15; in this case the lower part III of the column acts as a decantationcoalescence zone for the heavy phase. The light phase is discharged through lines 7 after passing through the upper part I which plays the role of

  Deactivation zone for the light phase.

  However, it is not necessary for the lower part III of the column to have a zone in the form of an inverted tulip, since it is also possible to draw off the mixture of the two phases which are not separated by the pipe 15 'and

  direct it to a decanter outside the column; at

  firing of this clarifier, the light phase is recovered and returned to the bottom of the column either through lines 13,

- or by the pipe 13 '.

  As an example, the following gives the results

  obtained during the functional tests of an annular column.

  according to the invention for the treatment of two phases consisting respectively of a nitric acid solution

  or by a nitric solution of uranyl nitrate which

  titrates the heavy phase, and by tributyl phosphate diluted

  % in dodecane, which constitutes the light phase.

  The column used had in its central part the following dimensions:

È-4 8 9 S. I

  - ring width: 8 cm, - diameter of the central cylindrical core - 29 cm,

  - height of the central part: 8 m.

  The packing consisted of annular stainless steel baffles with axial transparency

  25%, arranged as shown in the figure with a space-

e 40mm.

  It is specified that the axial transparency is defined at a baffle by the ratio of the section of the central portion II not occupied by the baffle on the section.

total of this central part.

  To verify the performance of the column, various tests were carried out at 30 C,

  continuous organic phase, ie continuous aqueous phase.

  In the case of these tests, efficiency was measured

  after establishing the profiles of the concentrations at

  In this column, this efficiency in height equivalent to a theoretical HETS stage has been evaluated. In addition, the total specific flows and the retention rate of the dispersed phase, which corresponds to the percentage

  volume of the dispersed phase present in the column.

  The results obtained are given in Table 1, hereinafter. For comparison, the same tests were carried out in this annular column but replacing the packing by a packing of perforated trays occurring all the section of the central part, constituted by nozzle trays made of stainless steel, whose hole diameter is

  3mm, 6mm pitch, spacing 50mm trays.

  The results obtained in this case are given

* in Table 2, below.

  In view of the results given in these two tables, it can be seen that the use of annular baffles makes it possible to very significantly improve the efficiency of the

annular column.

  Moreover, as a result of radioactive tracer measurements of the light phase and the heavy phase, it was possible to verify that the velocity profile was very dispersed with the nozzle plate packing while it was much more uniform with the lining

  with annular plates, used according to the invention.

TABLE 1

  Aqueous Solution Volume Ratio Flow Rate Asepecific phase aqueous phase of ETS Total retention content (m) U Organic phase norm 1.h-1 cm-2 (%) (g.1-1) - 3.98 0, 2 organic '2.0 11.2 0.66 - 4.0 0.2 aqueous 3.0 22.0 0r80 177 3.16 0.51 organic 2, 0 9.7 1.17 2.9 0.51 aqueous 2.0 18.0 0.56

TABLE 2

  Aqueous Solution Volume Ratio Flow Rates HETS-Specific Water Phase Content in-Respect Retention (m) U Organic Phase Standard 1.hl cm-2 (%) (g.271) (g.1.1 - 3.5 0.2 organic 1.67 8.8 2.0 173 3.1 0.51 organic 2.00 13.2 8.0 o rla co Ln "O -.- 1l

Claims (7)

  An annular pulsed column for countercurrently contacting two phases, at least one of which is a liquid phase, comprising an outer cylindrical casing (1) of vertical axis in which a cylindrical core (3) is disposed. delimiting inside said column with the outer casing (1) an annular section upper part (1) provided with means (5) for introducing a heavy phase and   means for evacuating (7) a light phase, a central part   the annular section (II) provided with a packing (21,23) for the countercurrent contacting of said phases, and a lower portion (III) of annular section provided with introduction means (13,13 '). ) of the light phase, of the evacuation means (15, 15 ') of the heavy phase and of means (11) for generating pulsations in the mixture of said phases, characterized in that said packing consists of annular plates (21 , 23) arranged horizontally and spaced from each other in the vertical direction, each   said trays occupying only part of the transpor-   of said central portion (II), said plates being distributed in a first series of plates (23) in contact by their periphery with the central cylindrical core (3) and in a second series of plates (21) in contact by their periphery with the outer casing (1) of said column, the trays of the first series being interposed between the trays of the second series.   Column according to Claim 1, characterized in that the central core (3) comprises an absorbent material or slowing down neutrons.   3. Column according to claim 2, characterized in that the central core (3) comprises a stack of   cylindrical bodies (3b) made of neutron concrete. _;   4. Column according to any one of the claims   1 to 3, characterized in that the means for generating the pulsations in the mixture of said phases comprise a pipe (11) opening laterally into the lower part (III) of said column. 5. Column according to claim 4, characterized in that the means for introducing the light phase are constituted by a pipe (13 ') opening into said tubing.   6. Column according to any one of the claims   1 to 5, characterized in that the upper part (I) comprises a zone having an annular section larger than that of the central part (II) and in that the means for evacuating the light phase consist of two diametrically opposed pipes (7) opening into said zone.   7. Column according to any one of the claims   1 to 6, characterized in that the lower part (III) of the column comprises an area having an annular section larger than that of the central part (II) and in that the means for evacuating the heavy phase are constituted by two diametrically opposite pipes (15) opening in said area.