Device For Dispersing Water-Soluble Polymers

Abstract

A device for dispersing a water-soluble polymer in powder form having a standard particle size of less than 1 mm, includes: a wetting chamber, a chamber for grinding and discharging the dispersed polymer with a horizontal axis of revolution, and a mechanism for connecting the wetting chamber to the grinding chamber in the form of an L-shaped tube. The upper and lower parts of the wetting chamber and the L-shaped tube have an internal surface with an identical surface tension (TS1). The cover of the wetting chamber has an internal surface with a surface tension (TS2) higher than the surface tension (TS1) of the internal surface of the upper and lower parts of the wetting chamber and the L-shaped tube.

Claims

1. A device for dispersing a water-soluble polymer in powder form having a standard particle size of less than 1 mm, comprising: a wetting chamber, into which the polymer is dosed, comprising a cylindrical upper part with a vertical axis of revolution extended by a conical lower part, said wetting chamber being further provided with: at least one opening formed in a thickness of a wall of the upper and/or lower parts, said opening emerging laterally into a connection to a primary water supply circuit, a cover provided with an opening formed in a thickness of a wall of said cover, said opening emerging into a connection to a source of powdered polymer, a chamber for grinding and discharging the dispersed polymer with a horizontal axis of revolution, said grinding chamber comprising: a rotor driven by a motor and provided with blades, said blades possibly being inclined with respect to the horizontal plane of the stator, a fixed stator in the form of a cylinder, in the wall of which a single row of vertical slots is cut over part of a height of said wall, over all or part of a periphery of the chamber, a ring fed by a secondary water circuit, the ring communicating with the grinding chamber so as to spray pressurized water onto the stator, an L-shaped tube connecting the wetting chamber to the grinding chamber, one end of which connects to the lower end of the wetting chamber and another end of which connects to an inlet of the grinding chamber, characterized in that the upper and lower parts of the wetting chamber and the L-shaped tube have an internal surface with an identical surface tension (TS1), and in that the cover of the wetting chamber has an internal surface with a surface tension (TS2) higher than the surface tension (TS1) of the internal surface of the upper and lower parts of the wetting chamber and the L-shaped tube.

2. The device according to claim 1, characterized in that a difference between the surface tension of the internal face of the cover (TS2) and that of the lower face of the upper and lower parts of the wetting chamber and the L-shaped tube (TS1) is at most 4 mN.Math.m.sup.−1.

3. The device according to claim 1, characterized in that a difference between the surface tension of the internal face of the cover (TS2) and that of the lower face of the upper and lower parts of the wetting chamber and the L-shaped tube (TS1) is 4 mN.Math.m.sup.−1.

4. The device according to claim 1, characterized in that the thickness of the wall in which the opening is formed emerging into the connection to the primary water supply circuit and the internal surface of said connection to the primary water supply circuit have a surface tension equal to (TS1).

5. The device according to claim 1, characterized in that the wetting chamber has an opening formed in the thickness of the wall of its upper part emerging laterally into an overflow and in that the thickness of the wall and the internal surface of said overflow have a surface tension equal to (TS1).

6. The device according to claim 1, characterized in that the thickness of the wall of the cover in which the opening is formed emerging into the connection to the source of powdered polymer and the internal surface of said connection to the source of powdered polymer have a surface tension equal to (TS2).

7. The device according to claim 1, characterized in that a material constituting the internal surface of the wetting chamber, its cover, including the thickness of the wall in which the openings are formed, and the internal surface of the L-shaped tube, is metal which has undergone a mechanical treatment capable of imparting to said surface a surface tension (TS1) or (TS2) respectively.

8. The device according to claim 1, characterized in that the material constituting the internal surface of the wetting chamber, its cover, including the thickness of the wall in which the openings are formed, and the internal surface of the L-shaped tube, is metal, and the internal surface is chemically modified so as to impart to said surfaces a surface tension (TS1) or (TS2) respectively.

9. The device according to claim 1, characterized in that the surface tension (TS1) is between 7.5 and 19.5 mN.Math.m.sup.−1 and the surface tension (TS2) is between 11.5 and 23.5 mN.Math.m.sup.−1.

10. The device according to claim 7, characterized in that the mechanical treatment is electropolishing.

11. The device according to claim 8, characterized in that the metal surface is chemically modified by a coating, the surface of said coating having a surface tension (TS1) or (TS2).

12. The device according to claim 1, characterized in that the blades of the rotor, at least in part, and the stator are made of stainless steel chosen from austenitic-ferritic or austenitic steels treated by vacuum nitriding or by carbon diffusion.

Description

FIGURES

[0040] FIG. 1 shows a 3D view of the device of the invention connected at its top to a metering screw for the polymer in powder form

[0041] FIG. 2 shows a plan view of the device for dispersing a water-soluble polymer in powder form with a standard particle size of less than 1 mm, comprising: [0042] a wetting chamber (1), into which the polymer is dosed, said chamber comprising: [0043] a cylindrical upper part with a vertical axis of revolution extended by a conical lower part, [0044] laterally, arranged on the lateral wall of the cylinder constituting the upper part of the chamber, [0045] two openings (3) each emerging into a means for connection to a primary water supply circuit in the form of a pipe (4), the axes of the openings being separated from one another by an angle of 45°, [0046] an opening (14) emerging into an overflow pipe (15), [0047] a cover (5) having an opening (6) emerging into a means for connection to a source of powdered polymer in the form of a tube (7). The tube (7) is connected to the metering screw (13). [0048] a chamber (8) for grinding and discharging the dispersed polymer with a horizontal axis of revolution, [0049] an L-shaped tube (2), one end of which connects to the lower end of the conical part of the wetting chamber, the other end connecting to the grinding chamber.

[0050] FIG. 3 shows a 3D view of the rotors and stators of the grinding chamber of the device. More precisely, the rotor/stator assembly comprises: [0051] a rotor (9) driven by a motor and provided with nine rounded blades (12), said blades being perpendicular to the horizontal plane of the stator but possibly able to be inclined with respect to the horizontal plane of the stator, [0052] a fixed stator (11) in the form of a cylinder, in the wall of which a single row of vertical slots (10) is cut over part of the height of said wall.

[0053] The following examples illustrate the invention without limiting its scope.

EXAMPLES OF EMBODIMENTS OF THE INVENTION

[0054] Counter-example: A device as described in FIGS. 1 to 3, in which the inner surface of the upper cylindrical and lower conical parts of the wetting chamber (1), the overflow pipe (15), the cylindrical elbow (2) and the cover (5), including the thickness of the wall of the chamber and the cover in which the openings (3, 6, 14) are formed, has a surface tension equal to 3 N.Math.m.sup.−1, has been put into operation. The inner surfaces (1), (2-6, 14) are metal without any chemical or mechanical treatment. Powder is observed to accumulate rapidly (within only a few days) on the inner surface of the tube of the wetting chamber and on the inner surface of the cover, causing the device to clog and stop.

[0055] Example 1: A device as described in FIGS. 1 to 3, in which the inner surface of the upper cylindrical and lower conical parts of the wetting chamber (1), the overflow pipe (15), and the cylindrical elbow (2), including the thickness of the wall of the chamber in which the openings (3, 14) are formed, has a surface tension equal to 13.5 N.Math.m.sup.−1, has been put into operation. The inner surface of the cover (5), including the thickness of the wall of the cover in which the opening (6) is formed, has a surface tension equal to 3 N.Math.m.sup.−1 (identical to the counter-example). The inner surfaces of the upper cylindrical and lower conical parts of the wetting chamber (1), the overflow pipe (15), and the cylindrical elbow (2), including the thickness of the wall of the chamber in which the openings (3, 14) are formed, are metal and have been chemically treated with Teflon® PFA (thickness 50 micrometres). Powder is observed to accumulate rapidly (within only a few days) on the inner part of the cover, eventually causing the PSU device to clog and stop. During this period, very slow or even zero accumulation of powder is observed on the inner walls of the cylindrical-conical tube.

[0056] Example 2: A device as described in FIGS. 1 to 3, in which the inner surface of the upper cylindrical and lower conical parts of the wetting chamber (1), the overflow pipe (15), and the cylindrical elbow (2), including the thickness of the wall of the chamber in which the openings (3, 14) are formed, has a surface tension equal to 13.5 N.Math.m.sup.−1 (as in example 1), and in which the inner surface of the cover (5) of the wetting chamber, including the thickness of the wall of the cover in which the opening (6) is formed, has a surface tension of 17.5 N.Math.m.sup.−1, has been put into operation. The inner surface of the cover (5) is metal and has been chemically treated with Teflon® PTFE (thickness 50 micrometres). Very slow or no accumulation of powder is observed on the inner surfaces of the upper cylindrical and lower conical parts of the wetting chamber and on the inner surface of the cover, over several weeks of operations.