Pulse column with filling for liquid-liquid extraction

Abstract

The invention relates to a pulse column (1) for liquid-liquid extraction, in particular a pulse column with a filling for liquid-liquid extraction, comprising a cylindrical tube (10) having a longitudinal axis (Z) and an inner diameter (D0), and a filling (20) located within the tube (10). The filling (20) comprises a rod (30) extending along a longitudinal axis (Z) and a plurality of cut-off discs (40) regularly distributed and fixed at a pitch (E) along the rod (30), each cut-off disc extending in a transverse plane (P) perpendicular to the rod (30), each of the cut-off discs (40) having, in the transverse plane (P), two arcs of a circle having a radius (R) as an outer edge of the cut-off disc, the two arcs are connected by two identical parallel rectilinear edges (41) spaced apart by a distance (D), any two of the adjacent cut-off discs (40) being oriented in a transverse plane (P) at a non-zero orientation angle (theta) relative to each other.

Description

Technical Field

[0001] The present invention belongs to the field of chemical engineering, more specifically to the field of liquid-liquid extraction. Among the various devices for continuously performing liquid-liquid extraction operations, pulse columns are known, which include a cylindrical tube and a set of fixed solid parts, which constitute obstacles to the movement of the liquid, called fillers and are contained in the tube. In operation, the tube is arranged vertically, and two immiscible liquids flow in opposite directions in the tube (the heavier liquid is introduced at the top and the lighter liquid is introduced at the bottom). Under the action of the pulse (oscillating motion applied to all liquids) and the filler, one of the liquids is dispersed in the other liquid in the form of droplets. This dispersion increases the contact surface between the two liquids, which enables one or more solutes originally contained in one of the liquids to be transferred to the other liquid.

[0002] Therefore, the present invention relates to a pulse column for liquid-liquid extraction, comprising a cylindrical tube having a longitudinal axis Z and an inner diameter D0, and a packing located inside the tube. Background Art

[0003] With regard to the filling contained in the tube, various solutions are known. Figure 4A In the first solution shown, the filler 120 is composed of a rod 130 and a series of regularly spaced elements 140 mounted on the rod 130, through which the rod passes. The rod 130 extends along a longitudinal axis Z, which is the longitudinal axis of the tube 110. The tube 110 is schematically shown in dotted lines. Each element 140 is a truncated disc 143, that is, the disc has a single rectilinear edge, the length of the single rectilinear edge is less than the diameter of the disc, and the rest of the outer circumference of the disc is a part of a circle. Each truncated disc 143 extends in a transverse plane (perpendicular to the longitudinal axis Z). The truncated discs 143 are arranged along the rod 130 so that any two adjacent truncated discs 143 are oriented 180° relative to each other (that is, if two adjacent discs 143 are arranged in the same transverse plane, the two adjacent discs will be symmetrical to each other relative to the longitudinal axis X). The distance between two adjacent truncated discs 143 is constant. This filler is called a "truncated disc filler".

[0004] However, in the case of small diameter tubes (e.g., about 15 mm in diameter), and / or in the case of liquids where the viscosity of one of the liquids is much greater than the viscosity of the other, packings with truncated disks are not efficient enough. Lack of efficiency means that the amount of material transferred between the two liquids is too small compared to an ideal theoretical mixer, and the column height is too large to obtain a given amount of material transfer. One reason for this inefficiency is often excessive axial mixing (along the longitudinal axis Z). This mixing is characterized by the axial dispersion coefficient D axThe higher this coefficient, the lower the efficiency of material transfer in the column. Thus, for a column with a diameter of 15 cm, the viscosity of one of the liquids is 8 cP (centipoise), and the total specific flow rate (TSFR) is 2 L / h / cm 2 (i.e., a total flow rate of 3.5 L / h for both phases), a pulse amplitude of 1.5 cm, a pulse frequency of 1 Hz (this test is referred to as the standard test), and for truncated disks spaced 2 cm apart, a 6.9 cm 2 Axial dispersion coefficient D ax .

[0005] In order to try to improve the efficiency of the column, a first solution was envisaged, which consists in reducing the distance between the elements 140. The tests carried out have shown that this configuration reduces the axial dispersion coefficient D of the column. ax For the standard test described above, a 2.1 cm 2 / sD ax , the D ax Lower than 6.9 cm for truncated discs spaced 2 cm apart 2 / sD ax value.

[0006] A second solution is also envisaged, such as Figure 4B As shown, in the second solution, the filler 120 is composed of two parallel rods 130 and a series of regularly spaced elements 140 mounted on the two rods, through which the two rods pass. These rods 130 extend along the longitudinal axis Z, which is the longitudinal axis of the tube 110. The tube 110 is schematically shown in dotted lines. The first type of element 140 is a ring 141 (a disc perforated at its center and having a hole to form a ring), and the second type of element 140 is a disc 142, the diameter of which is greater than the diameter of the hole in the ring 141 and less than the outer diameter of the ring 141. Each ring 141 and each disc 142 extend in a transverse plane P (perpendicular to the longitudinal axis Z). The rings 141 and the discs 142 are alternately arranged along the two rods 130, so that each disc 142 is located between two rings 141, and the distance between the ring 142 and the adjacent disc 141 is constant. This filler is called a "disc and ring filler". For the above standard test, and with the distance between the ring 142 and the adjacent disk 141 equal to 1 cm, a value of 3.5 cm was obtained. 2 / sD ax , the D ax Lower than 6.9 cm for truncated discs spaced 2 cm apart 2 / sD ax value.

[0007] However, tests conducted with the first and second solutions shown above indicate that there is a smaller range of values ​​of the operating parameters (pulse amplitude and frequency in the column, flow rate through the column) for satisfactory fluid dynamics than for configurations where the elements 140 are more spaced apart. In particular, the values ​​of the operating parameters (pulse amplitude and frequency in the column, flow rate through the column) for satisfactory fluid dynamics are smaller than for configurations where the elements 140 are more spaced apart. 最大 =3L / h / cm 2 ), for the first solution (DST 最大 =2L / h / cm 2 ) and the second solution (DST 最大 =1.8L / h / cm 2 ) before the column becomes blocked (i.e. when the two liquids cannot flow in opposite directions) DST 最大 Smaller. Summary of the invention

[0008] The present invention aims to remedy these disadvantages.

[0009] The present invention aims to propose a pulsed column for liquid-liquid extraction having a mixing efficiency which is as high as possible and a satisfactory hydrodynamic performance within a range of operating parameter values ​​which is as wide as possible.

[0010] This object is achieved by the following: the filler comprises a rod extending along a longitudinal axis Z and a plurality of truncated disks, the plurality of truncated disks being regularly distributed and fixed along the rod at intervals E and each truncated disk extending in a transverse plane P perpendicular to the rod, each of the truncated disks having, in the transverse plane P, two arcs of a circle with a radius R as outer edges of the truncated disk, the two arcs being connected by two identical parallel rectilinear edges spaced apart by a distance D, any two adjacent truncated disks being oriented at a non-zero orientation angle relative to each other in the transverse plane P.

[0011] By these provisions, mixing of the two liquids in the pulse column is achieved more efficiently. The hydrodynamic efficiency is satisfactory over a wider range of operating parameter values ​​than is the case with prior art packings.

[0012] For example, the spacing E between two adjacent disks is constant.

[0013] For example, the spacing E is of the same order of magnitude as the diameter D0 of the tube.

[0014] For example, the spacing E is smaller than the diameter D0 of the tube.

[0015] For example, the diameter D0 of the tube is less than 50 mm.

[0016] For example, the spacing E between two adjacent disks is equal to 10 mm and the diameter D0 of the tube is equal to 15 mm.

[0017] For example, the ratio between the transverse surface of the disk and the surface of the inner cross section of the tube is between 75% and 80%.

[0018] For example, at least the surface of the disk is made of a hydrophilic material.

[0019] For example, at least the surface of the disk is made of a hydrophobic material.

[0020] For example, a straight edge is jagged.

[0021] For example, the orientation angle is equal to 90°. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will be clearly understood and its advantages will best appear by reading the following detailed description of embodiments described by way of non-limiting examples. The description refers to the accompanying drawings, in which:

[0023] [Figure 1] Figure 1A is a side view of a pulse column for liquid-liquid extraction according to the present invention; Figure 1B It is along Figure 1A A cross section taken along line BB of FIG. 1 shows a truncation disk according to the invention.

[0024] [ Figure 2 ] Figure 2 yes Figure 1A A perspective view of a portion of a pulse column.

[0025] [ Figure 3 ] Figure 3 is a perspective view of another embodiment of a truncated disk of a pulse column according to the present invention.

[0026] [Figure 4] has been described Figure 4A is a perspective view of a portion of a pulse column according to the prior art; Figure 4B is a perspective view of a portion of another pulse column according to the prior art. DETAILED DESCRIPTION

[0027] Figure 1A A pulse column 1 is shown which enables continuous liquid-liquid extraction by vertical positioning of the pulse column 1 and circulation of two immiscible liquids in opposite directions in the pulse column 1 (heavier liquid introduced at the top, lighter liquid introduced at the bottom) and then pulsing (oscillating motion) the two liquids. For example, one of the liquids is aqueous (e.g. water) and the other liquid is organic.

[0028] The pulse column 1 comprises a cylindrical tube having a longitudinal axis Z and an inner diameter D0, and a filler 20 located inside the tube 10. The filler 20 comprises a rod 30 extending along the longitudinal axis Z and a plurality of truncated disks 40 regularly distributed along the rod 30. For example, the rod 30 is located at the center of the tube 10 and therefore has a longitudinal axis Z passing through the rod. For example, the rod 30 is cylindrical. The disk 40 is provided with a hole passed by the rod 30, and the disk is fixed to the rod 30 by any means (for example, by welding). Two adjacent disks 40 are spaced apart by a distance E (referred to as a spacing) measured along the longitudinal axis Z. For example, the spacing E is constant, i.e., the spacing is the same for any two adjacent disks 40. Each of the disks 40 extends in a transverse plane P (i.e., perpendicular to the longitudinal axis Z and therefore perpendicular to the rod 30).

[0029] Figure 1B It is along Figure 1A A cross section taken along line BB in FIG. 4 shows disk 40 in a transverse plane P of the disk. Each of disks 40 has, in transverse plane P, two arcs of a circle with radius R and center C as the outer edge of the disk, which arcs are separated and identical and connected by two identical parallel rectilinear edges 41 separated by a distance D. Therefore, disk 40 is truncated at two points and is symmetrical with respect to the center C of the disk, with the longitudinal axis Z passing through the center of the disk. The orientation axis A of disk 40 in plane P is defined as the transverse axis, which passes through the center C and is parallel to the rectilinear edges 41. Any two adjacent disks 40 (referred to as the first disk and the second disk) are oriented at a non-zero orientation angle 0 relative to each other in transverse plane P. As Figure 2 As shown, the orientation angle θ is the angle between the orientation axis A1 of the first disk 40 and the orientation axis A2 of the second disk 40 .

[0030] For example, the orientation angle θ is equal to 90°, such as Figure 2 As shown, any two adjacent discs 40 are at right angles relative to each other.

[0031] For example, the spacing E between two adjacent disks 40 is of the same order of magnitude as the diameter D0 of the tube 10. For example, the spacing E is smaller than the diameter D0 of the tube 10. For example, the diameter D0 of the tube 10 is smaller than 50 mm, for example, smaller than 15 mm. For example, the spacing E is equal to 10 mm.

[0032] The inventors conducted tests under the same operating conditions as the pulse column described above using prior art packing (standard test). Thus, for an inner diameter D0 = 15 cm, a spacing E = 1 cm and a viscosity of 8 cP (centipoise) for one of the liquids, a total specific flow rate (TSFR) of 2 L / h / cm 2(i.e., the total flow rate of the two phases is 3.5 L / h), the pulse amplitude is 1.5 cm and the pulse frequency is 1 Hz, the inventors obtained a 3.6 cm 2 / sD ax Regarding the use range, the maximum total specific flow rate (TSFR) DST obtained before column clogging 最大 Equal to 3L / h / cm 2 . D ax and DST 最大 These values ​​are superior to those obtained using prior art fillers.

[0033] The permeability of the filler 20 refers to the surface area (referred to as S L ) and the surface (referred to as S T )(and hence S T =π·(1 / 2D0) 2 ) ratio. The surface S left free for the liquid to pass through L For S L =S1+S2, where S1 is the surface of a ring with an outer radius 1 / 2D0 and an inner radius R, i.e. S1=(ST-πR 2 ), S2 is the removed surface of the disk 40. The removed surface S2 of the disk 40 is equal to the surface of the circle with a radius R minus the surface S of the disk 40 D (i.e. the surface of the disk 40 in a plane perpendicular to the longitudinal axis Z). Thus, the surface S of the disk 14 D For S D ={[α-sin(α)]·R 2}, where cos(α / 2)=D / 2R), where α is Figure 1B The angle of the truncated angular sector shown, D is the distance as defined above and shown in FIG1. ​​Thus, the removed surface S2 of the disk 40 is equal to S2 = πR 2 -S D Therefore, the transmittance is equal to S L / S T .

[0034] For example, the transmittance is between 20% and 25%. For example, the diameter D0 of the tube 10 is equal to 15 mm, the radius R of the disk 40 is equal to 7.25 mm and the distance D is equal to 10.55 mm, which gives a transmittance of 22%. A transmittance between 20% and 25% corresponds to a transverse surface S of the disk 40 of between 75% and 80%. D The surface S of the inner cross section of the tube 10 T The ratio S D / S T This is because ST =S D +S1+S2=S D +S L , so S D / S T =1-{transmittance}.

[0035] according to Figure 3 In the embodiment shown, the straight edge 41 of each disk 40 is serrated, that is, each straight edge 41 has serrations 415. The relief of the serrations 415 is visible to the naked eye and is different from the roughness, which is invisible to the naked eye. The serrations 415 are conducive to the formation of smaller droplets and help improve the mixing efficiency of the two liquids circulating in the tube 10.

[0036] The disk 40 may be made of any material. Advantageously, the material is hydrophilic (e.g., stainless steel), or at least the surface of the disk 40 is made of a hydrophilic material, which minimizes the adhesion of organic liquids to the disk 40 (operation is referred to as being in a "continuous aqueous phase"). Alternatively, the material is hydrophobic (e.g., a polymer such as PTFE), or at least the surface of the disk 40 is made of a hydrophobic material (e.g., the disk 40 is made of stainless steel coated with such a polymer), which minimizes the adhesion of water to the disk 40 (operation is referred to as being in a "continuous organic phase").

Claims

1. A pulse column (1) for liquid-liquid extraction, the pulse column comprising a cylindrical tube (10) having a longitudinal axis (Z) and an inner diameter (D0), and a packing (20) located inside the tube (10), the packing (20) being characterized in that the packing comprises a rod (30) extending along the longitudinal axis (Z) and a plurality of truncated disks (40), the plurality of truncated disks being regularly distributed and fixed at intervals (E) along the rod (30), and each truncated disk extending in a transverse plane (P) perpendicular to the rod (30), each of the truncated disks (40) having two arcs of a circle with a radius (R) as the outer edge of the truncated disk in the transverse plane (P), the two arcs being connected by two identical parallel straight edges (41) spaced apart by a distance (D), and any two of the adjacent truncated disks (40) being oriented at a non-zero orientation angle (θ) relative to each other in the transverse plane (P).

2. The pulse column (1) according to claim 1, wherein: The spacing (E) between two adjacent discs (40) is constant.

3. The pulse column (1) according to claim 2, wherein: The distance (E) is of the same order of magnitude as the diameter (D0) of the tube (10).

4. The pulse column (1) according to claim 2 or 3, wherein: The spacing (E) is smaller than the diameter (D0) of the tube.

5. The pulse column (1) according to any one of claims 1 to 4, wherein: The diameter (D0) of the tube (10) is less than 50 mm.

6. The pulse column (1) according to claim 5, wherein: Said spacing (E) is equal to 10 mm and said diameter (D0) of said tube is equal to 15 mm.

7. The pulse column (1) according to any one of claims 1 to 6, wherein: The lateral surface (S) of the disk (40) D ) and the surface (S) of the inner cross section of the tube (10) T ) ranges from 75% to 80%.

8. The pulse column (1) according to any one of claims 1 to 7, wherein: At least the surface of the disk (40) is made of a hydrophilic material.

9. The pulse column (1) according to any one of claims 1 to 7, wherein: At least the surface of the disk (40) is made of a hydrophobic material.

10. The pulse column (1) according to any one of claims 1 to 9, wherein: The straight edge (41) is serrated.

11. The pulse column (1) according to any one of claims 1 to 10, characterized in that The orientation angle (θ) is equal to 90°.

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