PULSED COLUMN FOR LIQUID-LIQUID EXTRACTION WITH PACKING

Abstract

A pulsed column for liquid-liquid extraction, including a cylindrical tube of longitudinal axis (Z) and inside diameter (D.sub.0) and packing located inside the tube. The packing includes a rod extending along the longitudinal axis (Z) and a plurality of truncated discs secured and regularly distributed along the rod with a separation (E) and each extending in a transverse plane (P) perpendicular to said rod, each of the truncated discs having, as their perimeter in the transverse plane (P), two arcs of a circle of radius (R) connected by two identical parallel rectilinear edges spaced apart by a distance (D), any two of the adjacent truncated discs being oriented with respect to each other in the transverse plane (P) by a non-zero orientation angle ().

Claims

1. A pulsed column for liquid-liquid extraction, comprising a cylindrical tube of longitudinal axis (Z) and inside diameter (D.sub.0) and packing located inside said tube, said packing being characterised in that it comprises a rod extending along said longitudinal axis (Z) and a plurality of truncated discs secured and regularly distributed along said rod with a separation (E) and each extending in a transverse plane (P) perpendicular to said rod, each of said truncated discs having, as their perimeter in said transverse plane (P), two arcs of a circle of radius (R) connected by two identical parallel rectilinear edges spaced apart by a distance (D), any two of said adjacent truncated discs being oriented with respect to each other in said transverse plane (P) by a non-zero orientation angle ().

2. The pulsed column according to claim 1, such that said separation (E) between two adjacent discs is constant.

3. The pulsed column according to claim 2, such that said separation (E) is of the same order of magnitude as said diameter (D.sub.0) of the tube.

4. The pulsed column according to claim 2, such that said separation (E) is less than said diameter (D.sub.0) of the tube.

5. The pulsed column according to claim 1, such that said diameter (D.sub.0) of the tube (10) is less than 50 mm.

6. The pulsed column according to claim 5, such that said separation (E) is equal to 10 mm and said diameter (D.sub.0) of the tube is equal to 15 mm.

7. The pulsed column according to claim 1, such that the ratio of the transverse surface (S.sub.D) of said disc to the surface of the internal cross section (S.sub.T) of said tube is between 75% and 80%.

8. The pulsed column according to claim 1, such that at least the surface of said discs is produced from a hydrophilic material.

9. The pulsed column according to claim 1, such that at least the surface of said discs is produced from a hydrophobic material.

10. The pulsed column according to claim 1, such that said the rectilinear edges are crenelated.

11. The pulsed column according to claim 1, wherein said the orientation angle () and is equal to 90.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1A and FIG. 1BFIG. 1A is a side view of a pulsed column for liquid-liquid extraction according to the invention; FIG. 1B is a cross section along the line B-B of FIG. 1A that shows a truncated disc according to the invention.

[0024] FIG. 2FIG. 2 is a perspective view of a portion of the pulsed column of FIG. 1A.

[0025] FIG. 3FIG. 3 is a perspective view of another embodiment of a truncated disc of the pulsed column according to the invention.

[0026] FIG. 4A and FIG. 4BFIG. 4A is a perspective view of a portion of a pulsed column according to the prior art; FIG. 4B is a perspective view of a portion of another pulsed column according to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

[0027] FIG. 1A illustrates a pulsed column 1 that enables liquid-liquid extraction continuously by the vertical positioning of this pulsed column 1 and the circulation of two non-miscible liquids in opposite directions in this pulsed column 1 (the heavier liquid being introduced at the top and the lighter liquid being introduced at the bottom) and then the application of a pulsing (oscillating movement) to these two liquids. For example, one of these liquids is aqueous (for example water) and the other liquid is organic.

[0028] The pulsed column 1 comprises a cylindrical tube 10 of longitudinal axis Z and inside diameter D.sub.0 and packing 20 located inside this tube 10. The packing 20 comprises a rod 30 that extends along the longitudinal axis Z and a plurality of truncated discs 40 regularly distributed along the rod 30. For example, the rod 30 is located at the centre of the tube 10 and therefore has the longitudinal axis Z passing through it. For example, the rod 30 is cylindrical. The discs 40 are provided with a hole through which the rod 30 passes and are secured to the rod 30 by any means, for example by welding. Two adjacent discs 40 are spaced apart by a distance E (referred to as the separation) measured along the longitudinal axis Z. For example, this separation E is constant, i.e. is identical for any two adjacent discs 40. Each of the discs 40 extends in a transverse plane P, i.e. perpendicular to the longitudinal axis Z and thus to the rod 30.

[0029] FIG. 1B is a cross section along the line B-B in FIG. 1A, which shows a disc 40, i.e. in its transverse plane P. Each of the discs 40 has as its perimeter in the transverse plane P two arcs of a circle of radius R and of centre C that are separate and identical and are connected by two identical parallel rectilinear edges 41 spaced apart by a distance D. The disc 40 is therefore truncated at two points, and is symmetrical with respect to its centre C through which the longitudinal axis Z passes. The orientation axis A of a disc 40 in the plane P is defined as the transverse axis that passes through the centre C and is parallel to the rectilinear edges 41. Any two adjacent discs 40 (called first and second discs) are oriented with respect to each other in the transverse plane P by a non-zero orientation angle . As illustrated in FIG. 2, the orientation angle is the angle between the orientation axis A1 of the first disc 40 and the orientation axis A2 of the second disc 40.

[0030] For example, the orientation angle is equal to 90, as illustrated in FIG. 2, i.e. any two adjacent discs 40 are at a right angle with respect to each other.

[0031] For example, the separation E between two adjacent discs 40 is of the same order of magnitude as the diameter D.sub.0 of the tube 10. For example, this separation E is less than the diameter D.sub.0 of the tube 10. For example, the diameter D.sub.0 of the tube 10 is less than 50 mm, example less than 15 mm. For example, the separation E is equal to 10 mm.

[0032] The inventors carried out tests under the same operating conditions of the pulsed column as described above (standard test) in the case of the use of the packings of the prior art. Thus, for a column with inside diameter D.sub.0=15 cm, a separation E=1 cm and one of the liquids with a viscosity of 8 cP (centipoise), a total specific flow rate (TSFR) of 2 L/h/cm.sup.2 (i.e. a total flow rate of the two phases of 3.5 L/h), a pulsing amplitude of 1.5 cm and a pulsing frequency of 1 Hz, the inventors obtained a D.sub.ax of 3.6 cm.sup.2/s. With regard to the range of use, the maximum total specific flow rate (TSFR) before congestion of the column DST.sub.max obtained was equal to 3 L/h/cm.sup.2. These values of D.sub.ax and of DST.sub.max are better than those obtained with use of the packings of the prior art.

[0033] Transparency of the packing 20 means the ratio of the surface left free for the liquid to pass at a disc 40, called S.sub.L, to the surface of the cross section (in a plane perpendicular to the internal longitudinal axis Z) of the tube 10, called S.sub.T, and which is therefore S.sub.T=.Math.(D.sub.0).sup.2. The surface S.sub.L left free for the liquid to pass is S.sub.L=S1+S2, where S1 is the surface of a ring of external radius D.sub.0 and of internal radius R, i.e. S1=(SR.sup.2), and S2 is the removed surface of a disc 40. The removed surface S2 of a disc 40 is equal to the surface of a circle of radius R minus the surface S.sub.D of the disc 40 (i.e. the surface of this disc 40 in a plane perpendicular to the longitudinal axis Z). The surface S.sub.D of the disc 14 is therefore SD={[sin()].Math.R.sup.2} with cos(/2)=D/2R) where is the angle of the truncated angular sectors, illustrated on FIG. 1B, and D is the distance defined above and illustrated in FIG. 1B. The removed surface S2 of a disc 40 is therefore equal to S2=R.sup.2S.sub.D. The transparency is thus equal to S.sub.L/S.sub.T.

[0034] For example, this transparency is between 20% and 25%. For example, the diameter D.sub.0 of the tube 10 is equal to 15 mm, the radius R of the disc 40 is equal to 7.25 mm and the distance D is equal to 10.55 mm, which gives a transparency of 22%. A transparency of between 20% and 25% corresponds to a ratio S.sub.D/S.sub.T of the transverse surface S.sub.D of the disc 40 to the surface of the internal cross section S.sub.T of the tube 10 of between 75% and 80%. This is because S.sub.T=S.sub.D+S1+S2=S.sub.D+S.sub.L and therefore S.sub.D/S.sub.T=1{transparency}.

[0035] According to an embodiment illustrated in FIG. 3, the rectilinear edges 41 of each disc 40 are crenelated, i.e. each rectilinear edge 41 has a crenelation 415. The reliefs of this crenelation 415 are visible to the naked eye and are distinct from roughness, roughness not being visible to the naked eye. This crenelation 415 favours the formation of smaller drops and contributes to increasing the efficacy of the mixing of the two liquids that are circulating in the tube 10.

[0036] The discs 40 can be produced from any material. Advantageously, this material is hydrophilic (for example a stainless steel), or at least the surface of the discs 40 is produced from a hydrophilic material, which minimises the adhesion of the organic liquid to the discs 40 (operation said to be in continuous aqueous phase). Alternatively, this material is hydrophobic (for example a polymer such as PTFE), or at least the surface of the discs 40 is produced from a hydrophobic material (for example the disc 40 is produced from a stainless steel covered with such a polymer), which minimises the adhesion of the water to the discs 40 (operation said to be in continuous organic phase).