EP1616627B1 - High gradient magnetic separator - Google Patents

Description

The invention relates to a high-gradient magnetic separator according to the preamble of the first claim.

The separation of ferro-, ferri- or paramagnetic particles from liquid or gaseous fluids by means of magnetic separators is a basic principle of process technology used in numerous variants. A particular advantage of the principle of magnetic separation is the ability to selectively separate magnetic particles from a mixture with other non-magnetic particles. The choice of the magnetic separator depends on the size and the magnetic properties of the particles.

Coarse strong magnetic particles, e.g. Magnetic ores with particle sizes> 75μm can then be separated with simple drum or belt separators. Fine, strongly magnetic particles can also be detected from aqueous suspensions up to a size of about 10-20 μm by means of special drum separators. For even finer particles in the micrometer range (about 0.1 to 20 microns), however, so far only so-called high-gradient magnetic separation is used.

The functional principle of high-gradient magnetic separators is based on the generation and bundling of strong field strength gradients by introducing a ferromagnetic matrix into an external magnetic field. The magnetizable elements of the matrix usually consist of disordered steel wool or ordered wire nets or profiled metal plates. They are magnetized by the external field and in turn form magnetic poles that reinforce or weaken the outer field in places. The resulting, high field strength gradients result in a strong magnetic force on para- or ferromagnetic particles in the direction of higher field strength. The Particles attach themselves to the induced magnetic poles of the matrix and are thus separated from the fluid.

Due to the possibility of generating very high field gradients and thus correspondingly high magnetic forces in connection with a fine-meshed matrix, the process of high-gradient magnetic separation is very effective when it comes to removing small amounts of magnetic impurities from a suspension. Typical applications are found in kaolinite processing or in the removal of corrosion products from condensate circuits.

After a certain period of operation, however, the loading of the separator with separated magnetizable particles are so high that the capacity of the magnetic separator is exhausted and a matrix cleaning is required. Usually, the matrix cleaning is carried out after switching off the magnetic field with a strong water jet or a backwash with high filter speeds. Due to the shape and structure of the matrix, which consists for example of steel wool or layered wire mesh and thus has numerous spaces, so-called dead volumes occur in the area of the matrix, ie areas which are not or only very slowly flowed through. In addition, the desire to keep the volume of the resulting rinse concentrate as low as possible and the maximum flow rate of the pump, the amount of flushing fluid used and the achievable flow rate during the flushing process. As a result, only incomplete cleaning is achieved. In particular, particles with a high remanent magnetization are difficult to remove again. The consequence is a further strong adhesion of these particles to the matrix wires, which significantly affects the cleaning efficiency.

While a large number of patents and publications are available on the subject of particle separation, there are only a few investigations in the field of filter backwashing and matrix cleaning. An effective and complete matrix deposition is essential for many applications, but also to meet technical, economic and environmental conditions. In particular, when the magnetic separation of magnetizable particles is involved as an important part of a continuous process, optimal filter operation requires a minimization of the duration of the matrix cleaning and the amount of flushing fluid required for this purpose.

In certain applications, for example in the wastewater sector, complete matrix cleaning is not absolutely necessary, but desirable and economically desirable to utilize the separator capacity. The matrix cleaning is carried out by rinsing water at high flow rates in countercurrent.

In the US 5,019,272 discloses a high gradient magnetic separator with a rotated filter housing with matrix, wherein the matrix is in the influence of a permanent magnet. The cleaning of the filter matrix takes place by means of a combination of pulsating inlet flow, centrifugal forces and an alternating magnetic field. The rotational movement in this concept, however, initially not for the purpose of energy input for cleaning available, but to generate a magnetic alternating field on permanent magnet.

Proceeding from this, it is an object of the invention to propose a high-gradient magnetic separator, which comprises a mechanically simple, robust, flexible and cost-effective device for efficient matrix cleaning.

The object is solved by the characterizing features in claim 1; the subclaims related thereto contain advantageous embodiments of this solution.

The invention consists of a high-gradient magnetic separator for the selective deposition of magnetisable particles from a suspension, comprising a matrix which can be positioned in a magnet system as a separation zone. The matrix is subdivided into plate-shaped partial volumes by plate-shaped magnetizable separation surfaces through which the suspension can flow. Furthermore, it has areas that serve as an inlet or as a drain of the suspension, wherein at least one, more preferably two separation surfaces are preferably arranged between an inlet and a drain. The matrix preferably extends over a closed volume, the inlets and outlets being formed by concrete lines into this volume. The separation surfaces are preferably formed by wire mesh or perforated metal foils or sheets, and may be provided with trapping structures for trapping forces from fluid flow or for clamping and securing.

For the selective separation of magnetic particles from a suspension, it is passed as a fluid flow via the inlet into the matrix and through this in at least one, preferably two separation surfaces. After passing through the separation surfaces of the fluid flow leaves the matrix through a drain, wherein the magnetizable particles are magnetically retained on the separation surfaces.

An essential design feature of the invention and with a particularly advantageous effect in matrix cleaning is the subdivision of the separation surfaces into at least two groups. The separation surfaces of each group are mechanically, for example via a housing, a carrier or a shaft rigidly coupled together and stored in the high gradient magnetic separator either fixed or movably mounted. The separation surfaces are preferably subdivided into two groups, wherein the group membership of the separation surfaces, which are preferably arranged parallel to one another in the matrix, alternates. In this case, a group is firmly inserted in the housing and the second group is jointly provided on a movably mounted carrier wherein an alternating arrangement of the separation surfaces of the different groups in the matrix. The movably mounted carrier is preferably motor-driven or actuator-driven, with the executable movement being cyclic, ie rotational and / or translationally oscillating in one or more directions. In a preferred embodiment, the carrier comprises a rotatably and / or laterally movably mounted shaft around which the matrix and the separation surfaces extend rotationally symmetrically. The frequency of the rotary or oscillating relative movement is usually between 5 and 1000 Hz, depending on the structural design.

For the selective deposition of magnetic particles from a suspension, the abovementioned mutually movable separation surface groups are not absolutely necessary. However, a moderate relative movement of adjacent separation surfaces to one another promotes the thorough mixing of the suspension and thus the more uniform detection of the entire suspension volume during the deposition and a more uniform separation of magnetizable particles on the available separation surfaces. From a certain strength, the relative movements prevent a stable settling of the particles on the separation surfaces, thus counterproductive and should be avoided during the deposition.

For a Matrixabreinigung required at certain intervals provide the aforementioned movable to each other Separation surface groups, however, represents a significant improvement.

The matrix cleaning is preferably carried out according to the countercurrent principle with a flushing fluid, wherein the relative movement of at least two of the aforementioned separation surface fractions to each other in the flushing fluid causes inertial forces, centrifugal forces, turbulence and shear forces, which detachment of magnetizable particles from the separation surfaces even in the presence of magnetic remanence or in the Influence of a magnetic field significantly improved or even only possible.

• Fig. 1 eine prinzipielle Seitenansicht eines Ausführungsbeispiels mit Elektromagnet,
• Fig. 2 eine prinzipielle Seitenansicht eines Ausführungsbeispiels mit Permanentmagnet,
• Fig. 3 eine Schnittansicht eines Ausführungsbeispiels mit fluidisch in Serie geschalteten Separationsringscheiben,
• Fig. 4 eine Schnittansicht eines Ausführungsbeispiels mit fluidisch parallel geschalteten Separationsringscheibe sowie
• Fig. 5 eine Aufsichtdarstellung der Separationsringscheiben.

The invention will be explained in more detail below with reference to exemplary embodiments with reference to the following figures. Show it

• Fig. 1 a schematic side view of an embodiment with electromagnet,
• Fig. 2 a schematic side view of an embodiment with permanent magnet,
• Fig. 3 a sectional view of an embodiment with fluidly connected in series separation ring discs,
• Fig. 4 a sectional view of an embodiment with a fluidic parallel separation ring disc and
• Fig. 5 a top view of the Separationsringscheiben.

As in Fig. 1 and 2 shown, the high-gradient magnetic separator 1 is in the immediate range of action of a magnet system 2, which serves as a field source. The magnetic field source is preferably electromagnets ( Fig. 1 ), superconducting magnet systems or even permanent magnet systems ( FIG. 2 ), wherein the high-gradient magnetic separator 1 is introduced into the magnet coil opening or between the pole shoes 3.

The actual high-gradient magnetic separator comprises a plurality of subunits, namely a substantially cylindrical housing 5, which is axially closed with a lid 6 and a bottom 7. A shaft 8 is mounted concentrically in the housing, in the embodiment in corresponding bearings 9 in the lid and / or bottom, sealingly rotatable and connected via a coupling 10 with a drive 11. Shaft, housing, cover and base plate are made of a non-magnetic material.

The core unit of the high-gradient magnetic separator is the matrix, which extends over the enclosed space enclosed by the housing 5, cover 6 and bottom 7 and in which the deposition of magnetizable particles takes place. The suspension (fluid) with the magnetic particles to be separated enters the high-gradient magnetic separator via the inlet 4 and is distributed over the separator cross-section. The actual separation takes place in the region of the matrix on Separationsringscheiben 13 and 14. The purified fluid stream leaves the high-gradient magnetic separator on the flow 12. inlet and outlet consist of several openings in the lid 6 and bottom 7 and have for better flow distribution in each case one conical shape.

The matrix is constructed according to the rotor-stator principle (cf. Fig. 3 and 4 ) and alternately comprises the aforementioned concentric arranged around the shaft and inserted in the housing 5 fixed and placed on the shaft 8 rotating separation ring discs 13 and 14, which divides the interior volume into rotationally symmetrical and axially successively arranged partial volumes.

The separation ring disks 13 and 14, in detail in FIG Fig. 5 each comprise a separation surface 15 of magnetizable material, preferably a wire mesh or a perforated metal foil or sheet, which can be flowed through by the suspension. The separation surface 15 is bounded by an outer and an inner stabilizing ring 16 and 17, respectively.

The rotating Separationsringscheiben 14 are mounted on the inner stabilizing rings 17 alternately with non-magnetic inner spacers 18 on the shaft 8 and clamped axially with a clamping sleeve 19. Likewise, the fixed Separationsringscheiben 13 are alternately inserted via the outer stabilizing rings 16 with non-magnetic outer spacer sleeves 20 in the housing 5 and clamped by a sleeve 21. The respective non-clamped inner and outer stabilizing rings 17 and 16 respectively form inner and outer spacer sleeves 18 and 20 an annular gap (see. Fig. 3 and 4 ).

Fig. 3 shows an embodiment with fluidly connected in series subvolumes in the matrix. In this case, both the sleeve 21 at the inlet 4 and the housing part, which is located at the outlet 12, a flow-optimized, in a first approximation conical shape. This avoids possible Totvolumnina especially in the corner regions of the matrix and thus possible mixing by retention and time-shifted re-mixing of individual fluid fractions in the matrix.

Fig. 4 represents an alternative concept with fluidically connected Teilvolumna in the matrix. In this embodiment, the feeding of the suspension with the magnetic particles to be separated takes place via a designed as a hollow shaft shaft 8 and a plurality of these branching radial inlet holes 22 as suspension outlets in each second of the partial volumes of the matrix. The flow of the purified fluid flow takes place from the partial volumes without direct inlet bore via drain holes 23, which open into a collecting channel 24, formed by the interior of a double-walled housing 25. Inlet and drain bores 22 and 23 are each arranged offset, so that when flowing through the matrix at least one separation ring disk is flowed through.

A matrix cleaning is done from time to time, preferably in countercurrent process. The criterion for the cleaning intervals is the pressure drop in the separator, which correlates with the loading of the sedimentation ring disks and indicates the need for matrix cleaning when exceeding a certain value. For the matrix cleaning a flushing fluid is passed from the flow through the partial volumes to the inlet, the shaft 8 are rotated with the rotating separation ring disks 13 at high speed (about 100 to 500 rev / min). The resulting shearing in the fluid flow creates turbulences which entrain the magnetic particles deposited on the separation ring disks. The separated particles will then be removed from the matrix by the superimposed purge fluid stream.

The efficiency of the cleaning can be further improved by the fact that the high-gradient magnetic separator 1 is deprived of the influence of a magnetic field. For this purpose, the magnetic field can now be switched off or the high-gradient magnetic separator can be removed from the magnetic field.

In addition to a rotational movement, an oscillation movement can alternatively be transmitted to the shaft 8. An additional force can be built up if the shaft oscillates axially by corresponding drive and bearing in addition to a rotational movement.

In addition to efficient Abreinigungsleistung and the separation process can be improved because superimposed on a slow rotational movement during the deposition process, the hydrodynamics in the filter can be influenced and thus a flow channel formation is suppressed.

The structure of the matrix proposed in the exemplary embodiments enables a modular and flexible construction of the high-gradient magnetic separator. Just by simply replacing the spacer sleeves 18 and 20, the number and spacing of the sub-volumes and separation ring disks can be varied in a simple manner and, according to a modular principle, also for subregions of the matrix. To minimize the pressure loss, for example, it is conceivable to choose larger distances between the matrix elements in the upper region of the high-gradient magnetic separator and to pack the matrix elements more densely in the lower region.

LIST OF REFERENCE NUMBERS

1

High gradient magnetic

2

magnet system

3

pole

4

Intake

5

casing

6

cover

7

ground

8th

wave

9

storage

10

clutch

11

drive

12

procedure

13

fixed separation ring disk

14

rotating separation ring disk

15

separation area

16

outer stabilization ring

17

inner stabilization ring

18

inner spacer sleeve

19

clamping sleeve

20

outer spacer sleeve

21

shell

22

inlet bore

23

drain hole

24

collecting duct

25

double-walled housing

Claims (9)

1. High-gradient magnetic separator (1) for the selective separation of magnetisable particles from a suspension, comprising a matrix which can be positioned in a magnet system (2) as a separation zone with at least one inlet (4, 22) and at least one outlet (12, 23) for the suspension, wherein the matrix is subdivided by plate-form magnetisable separation surfaces (15), through which the suspension can flow, into partial volumes arranged in relation to one another in rows,
   characterised in that
   the separation surfaces (15) are arranged alternately as fixed and moveable, wherein the moving separation surfaces are fixed on a moveably mounted carrier (8), wherein, when in operation, a relative movement of at least two of the aforesaid separation surfaces in respect of one another engenders in the flushing fluid introduced inertia forces, centrifugal forces, turbulences, and shear forces.
2. High-gradient magnetic separator according to claim 1, comprising a motor or actuator drive (10, 11) for the moveably mounted carrier.
3. High-gradient magnetic separator according to claim 1 or 2, characterised in that the separation surfaces (15) comprise a wire fabric or a perforated metal foil or a perforated metal sheet.
4. High-gradient magnetic separator according to any one of claims 1 to 3, characterised in that the carrier comprises a rotatable or laterally moveably mounted shaft (8), and the matrix and the separation surfaces (15) extend rotation symmetrically about the shaft.
5. High-gradient magnetic separator according to claim 4, characterised in that the separation surfaces are part of separation ring disks (13, 14).
6. High-gradient magnetic separator according to claim 4 or 5, characterised in that the matrix extends in an inner space volume of a cylindrical housing (5) with a base (7) and a cover (6), wherein at least one sealing bearing (9) for the shaft (8) is arranged in the cover or the base.
7. High-gradient magnetic separator according to claim 6, characterised in that the at least one inlet and the at least one outlet are arranged exclusively in the cover (6) or in the base (7).
8. High-gradient magnetic separator according to claim 6, characterised in that the housing (25) is a double-walled housing, with a collection channel (24), of which outlet holes (23) running radially inwards form the outlets, and the shaft (8) is a hollow shaft, which in the extension range of the matrix exhibits at least one radial inlet hole (22) serving as the inlet.
9. High-gradient magnetic separator according to any one of the preceding claims, characterised in that at least one of the separation surfaces (15) is arranged between the at least one inlet (4, 22) and the at least one outlet (12, 23).

Images