NL2034074B1 - Splitter plate for magnetic density separation - Google Patents
Splitter plate for magnetic density separation Download PDFInfo
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- NL2034074B1 NL2034074B1 NL2034074A NL2034074A NL2034074B1 NL 2034074 B1 NL2034074 B1 NL 2034074B1 NL 2034074 A NL2034074 A NL 2034074A NL 2034074 A NL2034074 A NL 2034074A NL 2034074 B1 NL2034074 B1 NL 2034074B1
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- 230000005291 magnetic effect Effects 0.000 title claims abstract description 111
- 238000000926 separation method Methods 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 claims abstract description 21
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- 238000004064 recycling Methods 0.000 claims description 4
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- 238000002474 experimental method Methods 0.000 description 17
- 230000007423 decrease Effects 0.000 description 6
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- 239000011554 ferrofluid Substances 0.000 description 5
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 239000012530 fluid Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 230000001154 acute effect Effects 0.000 description 2
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- 230000005298 paramagnetic effect Effects 0.000 description 2
- 230000002195 synergetic effect Effects 0.000 description 2
- 229910021380 Manganese Chloride Inorganic materials 0.000 description 1
- GLFNIEUTAYBVOC-UHFFFAOYSA-L Manganese chloride Chemical compound Cl[Mn]Cl GLFNIEUTAYBVOC-UHFFFAOYSA-L 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
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- 229910052742 iron Inorganic materials 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 235000002867 manganese chloride Nutrition 0.000 description 1
- 239000011565 manganese chloride Substances 0.000 description 1
- 239000002991 molded plastic Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C1/00—Magnetic separation
- B03C1/32—Magnetic separation acting on the medium containing the substance being separated, e.g. magneto-gravimetric-, magnetohydrostatic-, or magnetohydrodynamic separation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C2201/00—Details of magnetic or electrostatic separation
- B03C2201/20—Magnetic separation of bulk or dry particles in mixtures
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- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
A system (10) and method for magnetic density separation of a mixed stream of products (1) having different densities (Da,Db,Dc). At least one splitter plate (3) is arranged at a respective height in a separation chamber (8) and configured to split incoming product streams (1a,1b,1c) into separate channels (4a,4b,4c). The at least one splitter plate (3) is provided with one or more, preferably all, of the following characteristics: the convex cross-section profile of the front side (3f) is rounded, or at least any corners in the convex cross-section profile have obtuse inside angles (a); the front side (3f) is relatively thick, e.g. compared to a maximum size (Lp) of the products; and the splitter plate (3), at least at the front side (3f), is relatively smooth.
Description
Title: SPLITTER PLATE FOR MAGNETIC DENSITY SEPARATION
TECHNICAL FIELD AND BACKGROUND
The present disclosure relates to a system and method for magnetic density separation (MDS) of products, including further improvement of the splitter plates.
As background, WO 2017/111583 Al discloses an MDS system comprising a magnet configured to amplify a density gradient in a magnetic
Liquid for separating the products in the magnetic liquid according to their different density. One or more splitter plates are disposed along a product path where respective products travel through the magnetic liquid and used to separate product streams having different densities, thus floating at different heights in the magnetic liquid. The prior art aims to improve process continuity while maintaining a high separation efficiency, in particular by alleviating material build-up and clogging of products at the splitter and other surfaces with minimal disturbance to the process flow.
Thereto the prior art introduces a driving mechanism configured to drive the splitter plate with a reciprocating motion, preferably along a direction of the plate surface. By the reciprocating motion of the plate shape, a static friction of respective products coming into contact with the plate shape can be lowered or even completely cancelled. Accordingly, products may move more freely along their intended path over the plate shape by the resultant forces of drag, gravitation, and/or magnetism with less chance of getting stuck. Additionally, the prior art discloses that, by providing a wedge shaped plate (as seen in plan view), the reciprocating motion may not only be advantageous to move the products along its surface, but also to push products that would otherwise get stuck at the front edge of the plate facing the incoming product stream. In particular, the prior art discloses a V- shaped plate may be used to push the stuck product outward to a side of the channel where the products can be separately collected, e.g. by a collection chamber below the side of the plate.
There remains a need for further improvements to improve process continuity of known MDS systems and methods.
Aspects of the present disclosure relate systems and methods for magnetic density separation of a mixed stream of products having different densities. The system comprises a separation chamber configured contain a magnetic liquid. A magnetic field generator is configured to apply a magnetic field in the separation chamber for causing a density gradient in the magnetic liquid along a gradient direction. A product source is configured to introduce the mixed stream into the magnetic liquid contained in the separation chamber. The system is configured to pass the products along a product path direction through the density gradient for causing the mixed stream of products to be spread out along the gradient direction into product streams according to their different densities at different heights in the magnetic liquid. At least one splitter plate is arranged at a respective height in the separation chamber and configured to split incoming product streams into separate channels. Each splitter plate has a front side facing the incoming product streams. The front side extends along a plate width of the splitter plate in a channel width direction transverse to the product path direction and the gradient direction. The front side has a convex cross- section profile in a cross-section view of the splitter plate. Based on experiments, such as described herein, the inventors find that process continuity of the MDS systems and methods may be affected by blockage of products, in particular at the front side of the splitter plates. To alleviate these and other issues, the inventors have further optimized the designs of the splitter plates. The optimizations include rounding of the splitter plate front side, avoiding sharp edges, increasing the front side thickness, and lowering the surface roughness.
These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawing wherein:
FIGs 1A and 1B illustrate respective systems for magnetic density separation (MDS);
FIG 2A illustrates a perspective view of splitter plates separating different channels;
FIG 2B illustrates a cross-section view of a splitter plate, e.g. as indicated in any of FIGs 1A,1B,2A;
FIGs 3A-3C show images of an experiment using a test system with an initial design for the splitter plates having a pointed edge at the front side;
FIGs 4A-4C shows an illustration of the initial design splitter plate explaining how products may get stuck to the front side of the plate;
FIGs 5A-5C shows images of an experiment using an adapted design for the splitter plates having a rectangular front side;
FIGs 6A-6C shows images of experiments using different 3D printed designs of a rounded front side with different thickness and radius of curvature;
FIGs 7A-7C shows images of a further optimized design using a rounded front edge produced by molding;
FIGs 8A and 8B illustrates images comparing the same design rounded front edge but having different surface smoothness;
FIGs 9A-9C illustrate a time lapse in cross-section view of an improved design splitter plate where products have less tendency to get stuck to the front side of the plate;
FIGs 10A-10H illustrate various designs for front sides of splitter plates;
FIGs 11A-11D illustrate further designs of front sides.
Terminology used for describing particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and/or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features. It will be further understood that when a particular step of a method is referred to as subsequent to another step, it can directly follow said other step or one or more intermediate steps may be carried out before carrying out the particular step, unless specified otherwise. Likewise it will be understood that when a connection between structures or components is described, this connection may be established directly or through intermediate structures or components unless specified otherwise.
The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, the absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity.
Embodiments may be described with reference to schematic and/or cross- section illustrations of possibly idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relative terms as well as derivatives thereof should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless stated otherwise.
FIGs 1A and 1B illustrate respective systems 10 for magnetic density separation (MDS) of a mixed stream of products 1 having different (mass per volume) densities Da,Db,Dec. 5 Typically, an MDS system 10 comprises a separation chamber 8 configured contain a magnetic liquid L. Separation of the mixed stream of products can take place in the magnetic liquid L contained in the separation chamber 8. In some embodiments, e.g. as shown in FIG 1A, the magnetic
Liquid L may flow through the separation chamber 8. In other embodiments, e.g. as shown in FIG 1B, the magnetic liquid L may be statically held in the separation chamber 8. For example, the separation chamber 8 comprises a container, vessel, flow channel, et cetera. Typically, a magnetic field generator 2 is configured to apply a magnetic field in the chamber, 1.e. in the magnetic liquid L held therein. This causes a density gradient D in the magnetic liquid L, e.g. along a gradient direction Z as shown. It will be understood that the ‘density’ of the magnetic liquid L, as used herein, may refer to the effective (mass) density of the magnetic liquid L in relation to buoyant forces acting on the products, e.g. caused by pressure differences along the gradient direction Z. For example, the effective density of a respective region of the magnetic liquid L may correspond to the (mass per volume) density of respective products floating (in equilibrium) at a respective position (e.g. height along the gradient direction Z) in the respective region. Similarly, 1t will be understood that the ‘density gradient’ of the magnetic liquid L may refer to a gradient of effective densities, e.g. wherein the effective density changes as function of position along the gradient direction Z in the magnetic liquid L.
As described herein, a magnetic field generator 2 (or multiple) can be used to generate, amplify, reduce, and/or otherwise causes a density gradient D in the magnetic liquid L. In some embodiments, the magnetic field generator 2 comprises one or more permanent magnets and/or magnetizable material. In other or further embodiments, the magnetic field generator comprises one or more electromagnets. Also combinations are possible. So, the magnetic field generator 2 may comprise any type of magnet. Preferably, the magnets are arranged in an array with different orientations, e.g. with alternating up-down (NSNS) orientation of the magnetic field for subsequent magnets in the array, most preferably in a
Halbach array, e.g. with rotating orientation of the magnetic field NESW or
NWSE) for subsequent magnets in the array. In some embodiments, e.g. as shown, the magnetic field generator 2 is arranged below the magnetic liquid
L. In other or further embodiments (not shown), a magnetic field generator is arranged above the magnetic liquid L. Also other or further magnet configurations can be envisaged, e.g. a magnetic field generator adjacent the magnetic liquid L (not shown).
A magnetic liquid, e.g. a ferrofluid, is typically a liquid that contains suspended magnetic particles, such as iron or nickel. For example, these particles may be in the form of nanoparticles and may be coated with a surfactant to prevent them from aggregating and to keep them suspended in the liquid. Ferrofluids are typically composed of a liquid carrier and a suspension of magnetic particles. The liquid carrier is usually an organic solvent such as an oil, or water-based solutions. In principle any liquid that exhibits a (substantial) density gradient induced by a magnetic field may act as a magnetic liquid. is applied. For example, this may include paramagnetic fluids such as (a solution of) manganese(II) chloride (MnCly).
Without being bound by theory, the (effective) density gradient D of a magnetic liquid L may depend on a positional dependence of a magnetic field strength or density caused by the magnetic field generator 2. For example, a region with relatively high magnetic field strength or density may cause a relatively high pressure of magnetic particles accumulating in said region, corresponding to a relatively high density liquid; and a region with relatively low magnetic field strength or density may cause a relatively low pressure of magnetic particles accumulating in said region, corresponding to a relatively low density liquid. In a preferred embodiment, at least part of the magnetic field strength caused by the magnetic field generator 2 in the magnetic liquid L is non-linear, e.g. non-linearly changing as function of position in the magnetic liquid L. Most preferably, the magnetic field strength is an exponential function of a position or height (Z) in the magnetic liquid L, e.g. distance to the magnetic field generator 2. For example, an (ideal) Halbach array may exhibit a magnetic field that exponentially decreases as function of distance above a plane formed by the array. Typically, the corresponding density is proportional to the derivative of the magnetic field multiplied with the liquid strength (which depends on the magnetic field strength). For ferrofluids this is almost always non- linear. For a paramagnetic fluid such as MnCl: this is linear.
Preferably, the magnetic field strength is configured to cause a density gradient D, wherein the magnetic liquid L exhibits a set of different (effective) densities Da, Db, Dc at different positions (e.g. heights along the gradient direction Z) in the magnetic liquid L. Accordingly products 14,1b, lc of a respective (mass per volume) density may tend to move towards and/or (continue to) float (in equilibrium) at a respective height in the magnetic liquid L corresponding to the respective effective density Da,Db, Dec.
In some embodiments, e.g. as shown, respective products may tend to travel towards and/or along respective equidensity paths through the magnetic liquid L, e.g. wherein a density of the respective products 1a,1b,1c equals an effective density Da,Db,Dc of the magnetic liquid L at a respective position or height along the gradient direction Z. Once the products are at their respective equilibrium height, e.g. while traveling through the magnetic field, the (main) product path direction X may coincide with the equidensity lines of the magnetic liquid. For example, the products may then follow a path along a line or plane of effective density equal to their (mass per volume) density.
In some embodiments, e.g. as shown in FIG 1A, the product path direction X may be substantially horizontal. In other or further embodiments, e.g. as shown in FIG 1B, the product path direction X may be tilted, e.g. at least five degrees, preferably at least ten degrees, with respect to a horizontal plane. For example, the product path direction X may depend on an orientation and/or strength of the magnetic field, which may determine the density gradient D.
In the embodiments shown, the system 10 is configured to introduce the mixed stream into the magnetic liquid L and pass the products along a product path direction X through the density gradient D.
Preferably, this causes the mixed stream of products 1 to be spread out along the gradient direction Z into product streams 1a,1b,1c according to their different densities Da,Db,Dc at different trajectories or positions (e.g. heights) in the magnetic liquid L. In other or further embodiments, a fraction of relatively high density products lc may move towards a region of the magnetic liquid L near the magnetic field generator 2, e.g. a lower region and/or bottom of the magnetic liquid L. In other or further embodiments (not shown), a fraction of relatively low density products may move towards a region of the magnetic liquid near the magnetic field generator, e.g. a higher region and/or top of the magnetic liquid. Typically, when the magnet is positioned below the liquid, the corresponding density 1s altered such that it increases closer to the magnet; when the magnet is positioned above the liquid the corresponding density is altered such that it decreases closer to the magnet
In some embodiments, the system 10 comprises a conveyor belt 7 to collect a sinking fraction and/or products attracted to the magnetic field generator 2. Alternatively or in addition to high density products, products comprising magnetic and/or magnetizable material may be attracted to the magnet irrespective of their density. For example, metal parts may be mixed 1n a stream of plastic products. Preferably, the conveyor belt 7 comprises riffles for pushing products on the conveyor belt 5 along a respective product path. Alternatively, or additionally, the riffles may help to cause a flow in the magnetic liquid L. Alternatively, or in addition to the shown conveyor belt 7 at a bottom side of the magnetic liquid L, in some embodiments (not shown) a conveyor belt is provided in a top side of the magnetic liquid L. For example, the top side conveyor belt may help to transport a fraction of relatively low density products. For example, a channel can be formed between two or more conveyor belts. In one embodiment, e.g. as shown, the conveyor belt 7 may wrap around a respective magnetic field generator 2.
Alternatively, or in addition to fractions of relatively high density products 1c and low density products 1a, the mixed stream 1 may comprise one or more fractions of intermediate density products 1b that float in equilibrium at a respective height in the magnetic liquid L (between the products la and lc), e.g. where the effective density of the products 1b equals the effective density Db of the magnetic liquid L. In one embodiment, e.g. as shown each of the products 1a,1b,1c may float at a respective height corresponding to a respective effective density Da,Db, De.
In some embodiments, the system 10 comprises a product source 5, e.g. delivery channel configured to introduce the mixed stream 1 into the magnetic liquid L. In one embodiment, e.g. as shown, the product source 5 comprises a tube having an ending inside the magnetic liquid L. For example, the mixed stream of products 1 can be directly introduced in the magnetic liquid L. Optionally, the products can be mixed with magnetic
Liquid or other medium before introducing them into the MDS volume. In another or further embodiment (not shown), the product source can be located elsewhere, e.g. above the magnetic liquid L. For example, the mixed stream of products 1 can be introduced from above a surface level of the magnetic liquid L. Also other delivery mechanisms are possible, e.g. the mixed stream 1 can be introduced using a conveyor belt, e.g. the same conveyor belt 7 as shown or another belt (not shown).
In some embodiments, e.g. as shown in FIG 1A, the system 10 comprises a flow generator 6. Preferably, the flow generator 6 is configured to generate a laminar flow, e.g. avoiding turbulence in the magnetic liquid L may otherwise cause the products to stray from their equilibrium products paths. In one embodiment, the flow generator 6 comprises one or more laminators. For example, the laminator comprises an array of parallel tubes configured to causes a (laminar) stream of magnetic liquid over the magnetic field generator 2. For example, the product source 5 may be arranged between the laminators as shown. The product source 5 itself can also act as a flow generator instead of, or in addition to the flow generator 6.
In one embodiment, the flow generator 6 and/or product source 5 comprises a pump configured to pump the magnetic liquid L along the product path direction X. Alternatively, or in addition to a flow generator, the products may be propelled along their respective product path by gravity. For example, this may be the case for a tilted system as shown in FIG 1B. Also combinations of tilted systems with flow generators are possible.
In some embodiments, at least one splitter plate 3 is arranged at a respective height (e.g. position along the gradient direction Z) in the magnetic liquid L. For example, the one or more splitter plates 3 may form part of a splitter stage. Typically the splitter stage is arrange at or near an end of the product path, e.g. on an opposite side of the separation chamber 8 relative to the product source 5. In one embodiment, the one or more splitter plates 3 are configured to split incoming product streams 1a,1b,1c (e.g. incoming along the product path direction X) into separate channels 4a,4b,4c. Typically, each splitter plate 3 (or at least the front edge of the plate) is arranged at a respective position in the magnetic liquid L between respective product paths of products with different densities to be separated.
Preferably, the splitter plate 3 (or at least the front edge) extends at least partly in a plane corresponding a plane of equal (effective) density in the magnetic liquid L. By providing at least a front part of the splitter plate in the density gradient D, e.g. over the end of the magnetic field generator 2 and/or overlapping part of the magnetic field, the products may continue to travel along the splitter plate 3 (according to the equidensity lines/plane) and easily enter into the separate channels 44,4b,4c formed there between.
FIG 2A illustrates a perspective view of splitter plates 3 separating different channels 4a,4b,4c. FIG 2B illustrates a cross-section view P of a splitter plate 3, e.g. as indicated in any of FIGs 1A,1B,2A.
In one embodiment, e.g. as shown, each splitter plate 3 has a respective plate width Wp. For example, the plate width Wp can be measured along a width direction Y perpendicular to the density gradient D and main product path direction X. In another or further embodiment, each splitter plate 3 has a respective plate length Lp. For example, the plate length Lp can be measured along the product path direction X. While the splitter plates 3 are shown here as completely planar, also a curved splitter plate can be envisaged and/or an initial part of the splitter plate 3 can be connected to another part, e.g. at an angle, together forming part of a respective channel. In another or further embodiment, the splitter plate 3 has a plate thickness Tp, e.g. along the gradient direction Z and/or height direction of the density gradient D. For example, the plate thickness Tp may be constant or vary along a length and/or width of the plate. Typically, the plate thickness Tp is smaller than the plate width Wp and/or smaller than the plate length Lp, e.g. smaller by at least a factor ten, twenty, fifty, hundred, or more. For example, the plate thickness Tp (e.g. beyond the tip or frontside) is less than one centimeter, preferably less than half a centimeter, most preferably between one and three millimeter, or less. The thinner the plate, the less space it takes up in the channel and the more accurately a cut can be made between products of different densities. A thinner plate may also cause less disturbance on a stream of product and use less material.
In some embodiments, e.g. as shown, a set of channels 4a,4b,4c is formed using the one or more splitter plates 3 as boundaries and/or walls, e.g. upper and/or lower wall segments. Each channel has a respective channel height He, e.g. as measured along the gradient direction Z.
Preferably, the channel height Hc is more than the (maximum) plate thickness Tp, e.g. by at least a factor two, five, ten, or more. For example, one or more of the channels 44,4b,4c have a height between one and ten centimeter, or more; preferably between two and five centimeter. On the one hand, a minimum height of the channels, e.g. more than two centimeter, may allow relatively unobstructed passage of products. On the other hand, having multiple channels of relatively low height, e.g. less than three or four centimeters, may allow more fine grained separation of products with relatively small difference in densities.
Typically, each splitter plate 3 has a front side 3f, e.g. edge or rim, facing the incoming product streams 14,1b, lc. As illustrated in FIG 2A, the front side 3f preferably extends along a plate width Wp of the splitter plate 3 in a channel width direction Y transverse (e.g. perpendicular) to the product path direction X and the gradient direction Z. As illustrated in FIG 2B, the front side 3f preferably has a convex cross-section profile 3p in a cross-section view P of the splitter plate 3 (e.g. the cross-section view as seen along the channel width direction Y perpendicular to the plate width Wp).
In daily practice, while using MDS for separation of products, such as plastic recycling, the inventors have found that operation of the
MDS system can be unexpectedly interrupted. In particular the inventors have found that every now and then the liquid level drops in the separation channels (distributors). The inventors speculated that this level drop may be due to blockage in the splitter section. For example, in the MDS system used, the pump connected to the splitter section can take liquid from the distributor when the splitter section is blocked. However, such problems are difficult to observe in an MDS system because the ferrofluid, used as magnetic liquid, is black and completely opaque. Also, the system is normally closed. So, to get a better understanding of these and other issues, the inventors have performed experiments wherein the bottom part of the
MDS system was replaced with a transparent bottom plate, and using a transparent medium (e.g. water) instead of ferrofluid.
In each of the following described experiments the same test system was used. The test system comprises a normally used splitter stage having four splitter plates, one above the other. Each splitter plate has a plate thickness (Tp) of three millimeter. The channel height (Hc) was about ten times the thickness. Plastic flakes were continually present in the water which was pumped through the splitter stage. A camera was mounted below the transparent bottom plate to record the entrance to the splitter stage.
The camera recorded images for time periods up to forty-five minutes, or shorter when the splitter stage became blocked. These images at various instances of time (T) are shown in the following figures. Between the experiments, the inventors varied only the design of the cross-section profile 3p at the front side 3f of the splitter plates 3, as will be described in the following. These and other experiments were used for optimizing the present disclosed solutions pertaining to MDS systems and methods.
FIGs 3A-3C show images of an experiment using a test system with an initial design for the splitter plates 3. In the experiment, plastic flakes are flushing through the splitter stage of test system. As illustrated in the cross-section view P on the bottom right of each image, the splitter plates 3 in the initial design have a pointed edge at the front side 3f facing the incoming stream of products 1. For each image, also the time (T) is indicated in minutes since starting the experiment. As can be observed in
FIG 3B, the inventors find that in this design, initial blockage (indicated by ‘B’) starts to occur already after about 2 minutes (T=2min). As can be observed in FIG 3C, the material continues to pile up in front of the splitter plates leading to substantial blockage of the channels at 7 minutes.
FIGs 4A-4C shows an illustration of the initial design splitter plate 3 explaining how products 1 may get stuck to the front side 3f of the plate. Without being bound by theory, FIG 4A illustrates a product 1 floating towards the splitter plate 3 at approximately the same height; FIG 4B illustrates the product 1 contacting the front side 3f of the splitter plate 3; and FIG 4C illustrates the product 1 getting stuck to the front edge, e.g. partially wrapping around the edge. Further products may get stuck to the initially sticking product leading to the buildup of material which can eventually clog and/or block the channel. As illustrated, a typical splitter plate 3, as used in MDS, can have a relatively pointed or sharp edge at the front side 3f facing the incoming of stream of products 1. For example, the sharp edge can be useful to define a precise boundary between streams of different densities and/or cut the streams of liquid while minimizing turbulence and/or fluid resistance. However, the inventors have realized that the design of the front edge profile of a splitter plate can significantly affect the buildup of materials, such as products getting stuck at a relatively sharp edge. For example, the pointy edge of the initial splitter plate design may result in a relatively small contact area increasing friction and/or causing the products to hook and/or wrap around the edge. Similar problems may also occur when the splitter plate has other sharp edges and/or when the plate thickness Tp is relatively small, e.g. compared to product size Lp, even if there is no sharp edge. Furthermore, similar problems may also occur when the splitter plate, and in particular the front side 3f has a relatively high surface roughness Sr, e.g. increasing friction. These and other problems may be alleviated by the presently disclosed improvements of the splitter plate design, supported inter alia by the following experiments.
FIGs 5A-5C shows images of an experiment using an adapted design for the splitter plates 3 having a rectangular front side. As can be observed in FIG 5B, the inventors find that in this design, initial blockage starts to occur after about 5 minutes (T=5min). It will be appreciated that this is significantly later than for the initial design which was shown in FIG 3B at 2 minutes. As can be observed in FIG 3C, the material continues to pile up in front of the splitter plates leading to substantial blockage of the channels at around 13 minutes. This is also a significant longer compared to the initial design which was shown in FIG 3C at 7 minutes. Without being bound by theory, it is noted that the rectangular edge avoids the relatively sharp edge, i.e. acute angles, of the initial design, which may improve the avoidance of blockage for a longer time. Based on this insight, the inventors have tested various further rounded front edge designs, as shown in the following.
FIGs 6A-6C shows images of experiments using different 3D printed designs of a rounded front side with different thickness and radius of curvature. The 3D printed designs were mounted as the front edge onto the existing splitter plates 3. As illustrated in the cross-section view P on the bottom right of each image, the splitter plates 3 in the initial design have thickness of 3 mm, while the rounded front side has a thickness varying of 3 mm (FIG 6A), 6 mm (FIG 6B), and 9 mm (FIG 6C). Each of the shown designs having a fully rounded front side was found to be an improvement over the previous designs. Furthermore, it was found that the rounded designs having relatively larger thickness, e.g. 6 mm or 9 mm instead of 3 mm, resulted in further improvement. Without being bound by theory, this may be because the relatively thicker front side can be associated with a relatively larger front surface and/or relatively larger radius of curvature. This may help to further avoid specific pressure points where the products may get stuck. On the other hand, the larger thickness of the front side may diminish the capability of precisely distinguishing different densities of materials and/or lead to an overall smaller channel entrance height. Also, if the front side thickness becomes larger than the product size, the products may land in the middle of the front side without being pushed over or under the plate. So, the inventors find that the selection of optimal front side thickness can be a compromise between avoiding blockage and separation accuracy.
FIGs 7A-7C shows images of a further optimized design using a rounded front edge produced by molding. The molded design was mounted as a front side onto the existing splitter plates 3, similar to the 3D printed designs. Surprisingly, the inventors find that the molded design performs even better than the corresponding optimal 3D printed design of FIG 6B (front side thickness 6 mm). For example, FIG 7C illustrates that the molded design can continue to perform even after 45 minutes. Without being bound by theory, the further improved performance may be due to the increased smoothness associated with a molded design compared to the surface of the 3D printed designs.
It is noted that some blockage gradually builds up at the right side of the setup. However, this is be caused by the relative stagnancy of the water at the sides of the channel, and not an issue associated with the front side design. In some embodiment (not shown), the system comprises means for alleviating blockage at one or both sides of the channel. For example, the system may comprise a flow generator focused on the side of the channels, e.g. directing a flow at the front side 3f at the left and/or right side of the plate. Alternatively, or additionally, the system may comprises a mechanical pushing means at the top/bottom of the channel and/or at the sides of the channel and/or front side of the plates, e.g. conveyors, wheels, and/or riffles pushing products at the sides into the channels.
These and other issues of blockage could alternatively, or additionally, be alleviated by allowing a sideways path for the products, e.g. combining the present teachings with a wedge or V-shaped splitter plate (viewed along the gradient direction Z), as disclosed the previous publication
WO 2017/111583 Al which is discussed in the present introduction.
Alternatively, or additionally, the feature of one or more reciprocating splitter plates as disclosed in the previous publication could be combined with the present teachings to find further synergy. In particular, it will be appreciated that the reciprocating motion may help to alleviate especially the issue of products sticking along the length of the splitter plate, deeper in the channel, while the present teachings of an improved front side edge design may alleviate blockage in particular at the entrance to the splitter plate arrangement. For conciseness, the teachings of the previous publication are not repeated, but incorporated by reference herein it its entirety. So it will be understood that the present disclosed improved designs for the front side splitter plate can be applied in the embodiments as disclosed in the previous publication, and vice versa.
FIGs 8A and 8B illustrates images comparing the same design rounded front edge but having different surface smoothness. In FIG 8A the same molded design was used as in FIGs 7A-7C. To further investigate the effect of surface smoothness, the molded design was treated by sanding which resulted in a relatively rough surface as for the experiment shown in
FIG 8B. It will be noted that in the experiment with the relatively rough surface (FIG 8B), initial signs of blockage were observed relatively soon around 5 minutes (T=5min). This may be compared to the smooth design of
FIG 8A, where no signs of blockage were observed even up to 30 minutes (T=30min).
FIGs 9A-9C illustrate a time lapse in cross-section view P of an improved design splitter plate 3 where products 1 have less tendency to get stuck to the front side 3f of the plate. Taking into account the various experiments as discussed above have led to various preferred embodiments as discussed in the following.
In some preferred embodiments, the splitter plate 3, or at least the front side 3f has a relatively high thickness Tf. In one embodiment, the front thickness Tf is relatively high compared to the product size Lp. For example, the front thickness Tf is between 0.1 — 0.9 times the maximum or median product size Lp, preferably between 0.2 — 0.8 times, more preferably, between 0.3 — 0.7 times. In another or further embodiment, the front thickness Tf is at least three millimeter, at least four millimeter, at least five millimeter, at least six millimeter, e.g. up to nine millimeter, or more. The higher the front thickness, the higher may be the front surface facing the incoming products, e.g. reducing tendency of products to get stuck to the front side 3f. However, the relatively high thickness may also reduce accuracy for splitting different materials having relatively closely matching densities. So, in other or further embodiments, it may be preferred to keep the front side thickness Tf below a certain threshold, e.g. less than 30% of the channel height He, more preferably less than 20%, more preferably less than 15%, e.g. between 5 and 10%.
In some embodiments, e.g. as shown, the front thickness Tf corresponds to the overall plate thickness Tp. In other embodiments, (not shown here), the front thickness Tf may be higher than the plate thickness
Tp of rest of the splitter plate 3, e.g. higher by at least ten percent (factor 1.1), at least twenty percent (factor 1.2), at least fifty percent (factor 1.5), at least a factor two, or even a factor three, or more. For example, the front thickness Tf may be six or nine millimeter, while the overall plate thickness
Tp may be three millimeter. Advantageously, the relatively thin plate may help to save plate material while still reducing buildup of material due to a relatively thick front side edge. Furthermore, a synergetic advantage may be provided in that the relatively higher channel beyond the front side may prevent blockage deeper in the channel. In some embodiments, the front side thickness Tf can be defined as the (maximum) thickness of the plate as seen from the front side 3f, e.g. when viewed along the product path direction X. In other or further embodiments, the front side thickness Tf can be defined as the (maximum) thickness of the splitter plate 3 near the front side 3f, e.g. within a distance AX from the tip of the splitter plate (as measured along the product path direction X). In one embodiment, the distance AX may be the same or similar to an overall maximum thickness of the plate, e.g. within a factor one or two. For example, for a circular front side, as shown, AX may equal the radius R of the circle, which is half the maximum thickness. In another or further embodiment, the concept of what is near the front side 3f may be defined by a specific distance AX, e.g. ten centimeter, five centimeter, two centimeter, one centimeter, or half a centimeter. Most preferably, a maximum front side thickness Tf of the splitter plate 3, e.g. within a distance AX of one centimeter from the front side 3f, is at least half a centimeter.
In other or further preferred embodiments, the edge at the front side 3f of the splitter plate 3, e.g. within the distance X, is designed to avoid sharp edges. In one embodiment, the convex cross-section profile of the front side 3fis rounded, or at least any corners in the convex cross-section profile have obtuse inside angles a (as seen from inside the plate). By providing a relatively rounded surface and/or avoiding sharp edges, there may be less tendency for the products to get stuck to the front side 3f. In principle, the rounded front side 3f and/or front side avoiding sharp corners can be applied on a relatively thin splitter plate, to provide at least some of the advantages.
More preferably, this is combined with the relatively large front side thickness Tf to provide synergetic advantage. For example, a rounded relatively thick front side edge can provide a relatively large radius of curvature R which can optimally guide the products without sticking.
In other or further preferred embodiments, the splitter plate 3, or at least the front side 3f, e.g. within the distance AX from the tip, is provided with a relatively smooth surface. Preferably, the splitter plate 3 at least at the front side 3f has surface roughness “Ra” (i.e. average or arithmetic average of profile height deviations from the mean line) less than 25 micrometer (e.g. smoother than N11 according to ISO 4287:1997 standard), preferably less than 12.5 pm (e.g. N10), less than 6.3 pm (e.g.
N9), less than 3.2 pm (e.g. N8), less than 1.6 pm (e.g. N7), less than 0.8 pm (e.g. N6), less than 0.4 pm (e.g. N5), less than 0.2 pm (e.g. N4), less than 0.1 pm (e.g. N3), less than 0.05 pm (e.g. N2), down to 0.025 nm (e.g. Nl), or less.
For example, typical surface roughness (Ra) values for different finishes may include: rough machined finish (e.g. N10): Ra > 6.3 micrometers; machined finish (e.g. N9): Ra = 3.2 - 6.3 micrometers; ground finish (e.g.
N8): Ra = 0.8 - 3.2 micrometers; fine ground finish (e.g. N6): Ra =0.4-0.8 micrometers; honed finish (e.g. N5): Ra = 0.2 - 0.4 micrometers; polished finish (e.g. N4): Ra < 0.2 micrometers; buffed finish (e.g. N2): Ra < 0.05 micrometers. The smoother the surface, the less friction and/or tendency of the products to get stuck. For example, it may be preferred to provide the splitter plate 3 or at least the front side 3f with at least a ground finish (Ra<3.2pm), or smoother.
In principle, a relatively smooth surface can be applied on any splitter plate, e.g. by providing the splitter plate 3 with a smooth finish and/or coating layer. For example, the splitter plate 3 or at least the front side 3f can be provided with a layer of molded plastic, e.g. PET, or be composed entirely of such material, or provided with a smooth finish. In some embodiments, the front side 3f comprises a first material (e.g. plastic), connected to second material (e.g. metal) forming the rest of the splitter plate (3). In other or further embodiments, the splitter plate 3 at least at the front side 3f has an anti-stick coating. Most preferably, the relatively smooth front side surface is combined with a relatively thick front side and/or front side avoiding sharp edges to provide further synergy. For example, a relatively smooth rounded surface with large radius of curvature
R may provide an optimal design.
In some embodiments, the MDS systems and methods, as described herein, can be used for recycling a mixed stream of products and/or recovery of materials forming the products. In other or further embodiments, the products comprises plastic consumer products or parts thereof. In one embodiment, the products are relatively small, e.g. having a (maximum) cross-section product size Lp of less than ten centimeter, less than five centimeter, less than two centimeter, e.g. between one millimeter and one centimeter, or even less. The relatively small size may allow, e.g., the height Hc of the channel(s) as shown in FIG 2A, to be relatively small.
In some embodiments, the mixed stream of products 1 comprise parts of (consumer) products e.g. plastic packaging, containers, bottles, bags, et cetera that are cut and/or shredded into smaller parts before introducing these parts into magnetic liquid L. In other or further embodiments, the mixed stream of products 1 comprises flakes, e.g. formed of different plastic materials and/or having different mass densities to allow magnetic density separation as described herein.
In some embodiments, the stream of products comprises rigid products and/or material. For example, these may be rigid flakes over various shapes, including hooked shapes that may get stuck on the front side 3f of the splitter plate 3. In other or further embodiments, the stream of products comprises flexible products and/or material. For example, these may be products that can substantially bend and/or wrap around the splitter plate 3 touching the top and bottom sides of the plate of when impacting the front side 3f with the magnetic liquid L in normal operation of the MDS system. For example, the stream may comprise plastic products or flakes. It will be understood that relatively flexible materials, e.g. soft and/or thin plastic materials, may have a higher tendency to get stuck at the front side 3f of the splitter plate. For example, the flexible products and/or material may get stuck when wrapping around the front side 3f.
While it 1s appreciated that the present systems and methods provide particular benefit for the continuous operation of recycling plastics and/or soft materials, alternatively or additionally, also other or further products and materials can be recycled and/or separated for other purposes using the present methods and systems.
FIGs 10A-10H illustrate various designs for front sides of splitter plates 3. In each of the shown designs, except FIG 10F, the front side thickness Tf is relatively high. FIGs 10B and 10C show designs having relatively obtuse minimum angles amin. FIGs 10D — 10G show designs having a rounded front side 3f. FIGs 10G and 10H show designs wherein the front side thickness Tf is higher than the overall plate thickness Tp. In some embodiments, the convex cross-section profile of the front side 3f has no right angle corners or acute angle corners (e.g. all designs shown here except FIGs 10A and 10B). Preferably, any corners in the convex cross- section profile have obtuse inside (minimum) angles amin of more than 90 degrees, preferably at least 120 degrees, more preferably at least 135 degrees, e.g. up to 170 degrees, or more (close to 180 degrees for a circle). In other or further embodiments, the front side 3f of the splitter plate 3 has a rounded convex cross-section profile. Preferably, the rounded profile has a minimum radius of curvature Rmin (as seen from inside the plate) of at least 10% of the front side thickness Tf and/or maximum thickness Tp of the splitter plate 3. Preferably this is at least 25% (Rmin=Tf/4 as shown in FIG 10D), e.g. up to 50% (Rmin=Tf/2 as shown in FIG 10E and 10F), or more. In other or further embodiments, the splitter plate 3 has a front side thickness
Tf at the front side 3f and a plate thickness Tp further away from the front side 3f which is lower than the front side thickness Tf, e.g. by at least a factor 1.5 (e.g. as shown in FIGs 10G and 10H).
FIGs 11A-11D illustrate further designs for improvement of splitter plates 3. In some embodiments, the relatively high front side thickness Tf gradually decreases further away from the front side 3f. This may help to avoid turbulence. In other embodiments, e.g. as shown in FIGs 11A-11D, the front side thickness Tf abruptly decreases to promote turbulence and/or vortex creation around the front side 3f of the splitter plates. Preferably, the front side is shaped to created vortices shortly beyond the tip of the plates, e.g. to help loosen any stuck products at the front side 3f. Optionally, the cross-section shape of the front side 3f may vary along the channel width direction Y. In one embodiment, the cross-section shape at the sides of the channel abruptly decreases further away from the front side and/or is configured to generate vortices at the sides of the channel. In another or further embodiment, the cross-section shape in the middle of the channel decreases further away from the front side and/or is configured to avoid turbulence.
In interpreting the appended claims, it should be understood that the word "comprising" does not exclude the presence of other elements or acts than those listed in a given claim; the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several "means" may be represented by the same or different item(s) or implemented structure or function; any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise.
Claims (15)
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| NL2034074A NL2034074B1 (en) | 2023-02-02 | 2023-02-02 | Splitter plate for magnetic density separation |
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| NL2034074A NL2034074B1 (en) | 2023-02-02 | 2023-02-02 | Splitter plate for magnetic density separation |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU607593A1 (en) * | 1973-07-05 | 1978-04-24 | Ворошиловградский Филиал Государственного Проектно-Конструкторского И Научно-Исследовательского Института По Автоматизации Угольной Промышленности | Magnetohydrodynamic separator |
| SU1701387A1 (en) * | 1989-12-04 | 1991-12-30 | Предприятие П/Я А-1758 | Magnetohydrostatic separator |
| WO2014158016A1 (en) * | 2013-03-25 | 2014-10-02 | Technische Universiteit Delft | Magnet and device for magnetic density separation |
| WO2017111583A1 (en) | 2015-12-21 | 2017-06-29 | Feelgood Metals B.V. | Splitter for magnetic density separation |
-
2023
- 2023-02-02 NL NL2034074A patent/NL2034074B1/en active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU607593A1 (en) * | 1973-07-05 | 1978-04-24 | Ворошиловградский Филиал Государственного Проектно-Конструкторского И Научно-Исследовательского Института По Автоматизации Угольной Промышленности | Magnetohydrodynamic separator |
| SU1701387A1 (en) * | 1989-12-04 | 1991-12-30 | Предприятие П/Я А-1758 | Magnetohydrostatic separator |
| WO2014158016A1 (en) * | 2013-03-25 | 2014-10-02 | Technische Universiteit Delft | Magnet and device for magnetic density separation |
| WO2017111583A1 (en) | 2015-12-21 | 2017-06-29 | Feelgood Metals B.V. | Splitter for magnetic density separation |
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Owner name: MYNEIP B.V.; NL Free format text: DETAILS ASSIGNMENT: CHANGE OF OWNER(S), ASSIGNMENT; FORMER OWNER NAME: URBAN MINING CORP B.V. Effective date: 20241227 |