Patent Application
20190201913
The invention relates to an apparatus for removing magnetizable particles in a substance by means of magnetic separation. The invention further relates to a device for pre-magnetizing magnetizable particles. Furthermore, the invention relates to a method of removing magnetizable particles from a substance by means of magnetic separation.
The application of substances such as paint, primer, degreasing and rinsing fluids to surfaces is a common manufacturing step across a diverse range of industries, such as automobile manufacturing. Some techniques for applying substances to surfaces include spray painting, spray coating, airbrushing and dip coating. In implementing these techniques, it is desirable to have compositions which are substantially free from impurities.
However, such compositions become contaminated due to, for example, the actual manufacturing process i.e. welding, shaving, drilling, deburring etc. or from displacement along conveying equipment such as pipes or tubes which may release particles as a result of friction with the substance or by contact with the painted object. Such particles which are inherent to the manufacturing process, will have a negative impact on the quality and finish of the application, and can lead to issues such as rust formation (in the case of iron particles), and gaps in a coloring or functional coating/finish due to the interfering particles.
Therefore, such substances are commonly treated prior to or during application in order to remove undesirable particles.
Magnetic separation is one technique which is employed in the removal of metallic particles, and which involves the application of a magnetic field within a substance resulting in magnetization, the metallic particles are drawn from the substance and onto a particle collecting element.
However, this technique has proven less effective in the removal of particles of a smaller size and of particles of a paramagnetic material, which are more resistant to magnetization. This is the case, for example, with (sub)micron-sized particles or for mixed steel/aluminum production. Recent advances in technology have led to development of increasingly thinner coatings applied to compositions. This requires more efficient filtration methods of the substances especially in the lower micron-size range of impurities. Smaller particles are less susceptible to the regular magnetic fields in separators, such that these smaller particles remain in the substance flow and may cause damage and/or failure in the long run.
Therefore, there is a need for separation techniques which can achieve particle removal at a higher resolution or degree, and which provides removal that is effective throughout a broader range of particle sizes and materials.
It would therefore be desirable to provide an improved apparatus for separating particles from a substance that alleviated some or all of the above problems. Therefore, it is an object of the invention to provide an improved device and method by which to effectively remove metallic impurities or contaminants from a substance, and in particular particles of a relatively small size.
This is achieved by providing an apparatus for removing magnetizable particles in a substance, the apparatus comprising:
a magnetic separation chamber for filtering magnetizable particles and flocs from the substance, wherein the magnetic separation chamber comprises a first housing that defines a first space through which the substance can flow, as well as at least one first magnet of which a first magnetic field reaches into the first space, and which first magnet is located within a first holder that has an interface with the first space; and
a flocculation chamber for inducing flocculation of the particles in a substance, the flocculation chamber being in fluid connection with the magnetic separation chamber;
wherein the magnetic separation chamber is located downstream of the flocculation chamber, and wherein the flocculation of the magnetizable particles results in magnetizable flocs, and the magnetic field of the first magnet causes the magnetizable flocs to be attracted towards the first magnet, thereby removing the flocs of magnetizable particles from the substance.
By forcing the magnetizable particles to form flocs, the magnetizable parts, i.e. particles and/or flocs, to be removed by the magnetic separator will be larger than the original magnetizable particles. In particular for (sub)micron-sized particles or paramagnetic particles, the magnetic separator can have problems removing these particles without any pre-treatment to increase the removal efficiency. By floccing these small particles together, the magnetic field of the magnet in the magnetic separator, i.e. the first magnet, is large enough to get hold of the flocs and to separate the flocs from the substance. Floccing may be achieved by the addition of inorganic electrolytes or polymers, or by magnetic flocculation.
In an embodiment, the flocculation chamber comprises a second housing that defines a second space through which the substance can flow, as well as at least one second magnet of which a second magnetic field reaches into the second space, and which second magnet is located within a second holder that has an interface with the second space, and wherein the magnetic field of the second magnet causes the magnetizable parts to be attracted to each other, thereby undergoing flocculation and forming flocs.
A preferred way to form flocs of the magnetizable particles is by means of a second magnetic field induced by a second magnet in the flocculation chamber. The second magnetic field is large enough to magnetize the particles enough to floc together and form flocs, i.e. larger magnetizable parts. Preferably, the flocculation chamber is arranged immediately adjacent to the magnetic separation chamber. This may be achieved when the flocculation chamber and the magnetic separation chamber are integrally formed, this can be by using flanges, welds, glue or any other sort of connections. They can be separate parts or a monolithic integral element.
In that case the flocs formed in the flocculation chamber travel only a short distance. The rate of flocculation is determined by the interplay between the dipolar magnetism induced by the magnetic field that flocs the particles, and the hydrodynamics of the substance flow that tend to disintegrate the flocs.
When the applied magnetic field is large enough, the attractive magnetic energy will be greater than the sum of the repulsive energy and the particle will tend to form aggregates, i.e. flocs. Another condition to be satisfied is that the time needed to floc is smaller than the residence time of the particles in the second magnetic field. The second magnetic field should not be too large in combination with a too low substance flow, as the flocculation chamber may then act as magnetic separator.
The adhesion strength of the aggregates or flocs must be adequately large to prevent them from breaking up by the fluid shear stress induced by the hydrodynamics of the substance flow. To efficiently counteract this disintegration, the flocculation magnetic field, i.e. the second magnetic field, in the flocculation chamber has to be designed in such a way that the flocculating magnetic field is kept at a minimum distance from the main magnetic field, i.e. the separating or first magnetic field.
Furthermore, in a turbulent flow the flocs will undergo more disintegration forces than in a laminar flow. Maintaining a laminar flow between the flocculation field and the main separation field is another condition to be satisfied.
In order to have the first and/or second magnetic fields extend into the first and/or second space, the first and/or second holders may extend into the first and/or second spaces, respectively. Preferably, each first and/or second holder comprises a tube that is closed at an end that extends into the first and/or second space, respectively.
In that case, the first and/or second magnets may have a rod shape, that have a releasable fit into the first and/or second holder. As the magnets extend into the space, the respective magnetic fields also extend into the space of the chambers, being the flocculation and/or magnetic separation chamber.
The first and/or second holder may have a top side from which each tube extends into the first and/or second space, respectively. The magnetizable particles or flocs may accumulate now on the outside of the first and/or second holders, as a result of which the magnets themselves are not exposed to the substance and/or the magnetizable particles.
Preferably, the first and/or second magnets are connected to a moving mechanism to move the first and/or second magnet with respect to the first and/or second space, respectively. The moving mechanism can remove the first and/or second magnet from the holder. As a result of removing the magnet from the holder, the magnetic field in the space is removed or at least decreased in strength so that the holder can be cleaned in a simple manner.
The housing of the magnetic separation chamber may further comprise a removable attachment, wherein the magnetic elements of the magnetic separation chamber are connected to the attachment. The housing further comprises one or more holders for respectively holding the one or more magnetic elements.
When the magnets are raised out of their holder, the magnetic field decreases considerably in the liquid in the magnetic space, as a result of which the particles accumulated on the outside of the holders can easily be removed. In order to ensure that the material does not enter the cleaned liquid again, a bottom wall of at least one of the chambers may be provided with a discharge for removing magnetizable parts which have accumulated on the outside of each tube.
According to an embodiment, the housing of the flocculation chamber is provided with an inlet part that is connectable to a conduit system through which the substance flows, and wherein the housing of the magnetic separation chamber is provided with an outlet part that is connectable to the conduit system. Preferably, the inlet part widens out to the flocculation chamber to decrease a flow rate of the substance flowing into the flocculation chamber.
For the particles to form aggregates or flocs in the flocculation field the magnetic field of the second magnet has to be sufficiently large and the time the particles spend in the flocculation field should be longer than the time it takes to form aggregates from the particles. The residence time of the particles in the flocculation field is increased by an enlarged diameter of the inlet with respect to that of the conduit system. This reduces the flowrate of the substance and therefore increases the residence time of the particles in the flocculation field. Preferably, the second magnetic field is low enough to prevent the particles to accumulate on the second holder, but high enough that the particles are magnetized and thereby attracted to each other to form aggregates.
After the magnetic separation chamber, the substance may flow into the conduit system again. Therefore, the outlet part may taper away from the magnetic separation chamber. The outlet part then again reduces the diameter of the piping to be compatible with the conduit system.
The first space of the magnetic separation chamber may define a spatial volume which is greater than the spatial volume defined by the second space of the flocculation chamber. The larger the spatial volume of a chamber, the more the flow rate is reduced and the longer the residence time in the chamber. As such, the residence time in the magnetic separation chamber may be longer than that in the flocculation chamber. This is to increase the separation efficiency of the magnetic separation chamber by allowing more time for accumulation of the parts on the first holder.
A longitudinal direction of the one or more first and/or second holders may be substantially perpendicular to a downstream direction from the flocculation chamber towards the magnetic separation chamber. Additionally or alternatively, a direction of the first and/or second magnetic fields may be substantially perpendicular to the downstream direction.
Alternatively, the longitudinal direction of the one or more first and/or second holders may be substantially parallel to a downstream direction from the flocculation chamber towards the magnetic separation chamber. Additionally or alternatively, a direction of the first and/or second magnetic fields may be substantially parallel to the downstream direction.
Alternatively, the longitudinal directions of the one or more first and/or second holders may differ, such that the holders are arranged in a combination of substantially perpendicular and substantially parallel longitudinal directions with respect to the downstream direction from the flocculation chamber towards the magnetic separation chamber. Additionally or alternatively, a direction of the first and/or second magnetic fields may comprise a combination of substantially perpendicular and substantially parallel directions with respect to the downstream direction.
As used herein, longitudinal direction refers to that direction along which a length of the respective element is greatest, that is, the direction along the long axis of a body.
To counteract the disintegration of the aggregates formed in the flocculation field the distance of this field to the main separation field is kept at a minimum and the flow pattern is kept within a regime of unseparated flow. The flocculation field is mounted as close as possible to the magnetic separation chamber with the main separation field. With an average incoming flow velocity of between 1-4 m/s, preferably about 2 m/s, the time between leaving the flocculating magnetic field and reaching the main separating magnetic field is between 0.1 and 1 second, preferably between 0.1-0.4 second. The magnitude of the magnetic field provided by each of the one or more first magnets of the magnetic separation chamber may be between 0.03 and 1 Tesla.
A cross section of the second holder of the second magnet has a greater dimension in the downstream direction with respect to a dimension in a direction transverse to the downstream direction. In order to keep a laminar flow between the flocculation field and the main separation field the outer tubes of the flocculation unit have a major dimension in the downstream direction. Preferably, the second holder of the second magnet has an oval cross section, wherein a major axis of the oval cross section is directed in the downstream direction. Computational Fluid Simulations on this design have proven that the use of oval shaped tubes significantly contribute to maintaining a laminar flow at Reynolds numbers smaller than 5.
The cross section of the first magnets may be circular. However, the cross section of the first and/or second magnets may be any kind of shape suitable for magnetic separation or flocculation. The cross section of the first and/or second holders may be similar to that of the respective magnets. Alternatively, the first and/or second holders have distinct cross section from that of the respective magnets.
The flocculation chamber may be configured to induce flocculation of particles in the smaller range of particles present in the substance, preferably having a size equal or smaller than 15 micrometer, more preferably of particles having a size in the order of 3 to 10 micrometers.
In magnetic separation of alkaline degreasing fluids, the process of magnetic flocculation plays a positive role by increasing the efficient recovery of ferritic particles from 3 to 15 micron. The effect for paramagnetic particles will be relatively lower albeit still enhances capturing these particles in the matrix of ferromagnetic particles. The process of magnetic flocculation may also play a positive role in the recovery of ferromagnetic of other sizes, as well as recovery of paramagnetic particles.
The invention further relates to a device for pre-magnetizing magnetizable particles, the device comprising a flocculation chamber for inducing flocculation of the particles in a substance, the flocculation chamber being fluidly connectable to a magnetic separation chamber located downstream from the flocculation chamber, wherein the flocculation chamber comprises a housing that defines a space through which the substance can flow, as well as at least one magnet of which a magnetic field reaches into the space, and which magnet is located within a holder that has an interface with the space;
wherein the magnetic field of the magnet causes the magnetizable particles to be attracted to each other, thereby undergoing flocculation and forming flocs.
By having the process medium flow through the flocculation field first, the medium and the pollution in the medium will be distributed more evenly through the magnetic separation chamber. Because of this better medium distribution the flow velocity in the magnetic separation chamber will be reduced, which leads to more efficient separation.
The device may further comprise an inlet part that is connectable to a conduit system through which the substance flows; and one or more flanges for connection to the magnetization chamber. Preferably, the inlet part widens out into the flocculation chamber to decrease a flow rate of the substance flowing into the flocculation chamber. The residence time of the particles in the flocculation field is increased by an enlarged diameter of the inlet with respect to that of the conduit system. This reduces the flowrate of the substance and therefore increases the residence time of the particles in the flocculation field.
The device may be an (integral) part of a magnetic particle separation system or the device is configured for retrofitting into a magnetic separation system, an existing magnetic separation system or any other system, method, or technology for separation, for instance by combination with a pre-installed magnetic separator chamber.
The invention furthermore relates to a method of removing magnetizable particles from a substance, the method comprising the steps of:
The method may further comprise the step of inducing flocculation providing a second magnetic field applied in the flocculation chamber. Forming the flocs is thus done by means of magnetic flocculation.
Preferably, the method comprises the step of reducing a flow rate of the substance prior to and/or during the step of forming flocs. By reducing the flow rate of the substance, the time for forming flocs, i.e. the residence time in the flocculation chamber, is increased and the flocculation efficiency is increased.
After the flocculation and the separation step, the method may further comprise cleaning the magnetic separation chamber and/or the flocculation chamber. During the process, some of the magnetizable particles may adhere in the respective chamber. This may impair the flocculation and/or separation process. Cleaning the respective chamber will enhance the efficiency of the further separation process. Preferably, cleaning any of the chambers comprises removing the respective magnets from the chamber. By removing the magnetic field from the respective chamber, the magnetizable particles remaining there will not be under the influence of the magnetic field anymore. Thus, the cleaning process of the respective chamber is facilitated. Further, cleaning of any of the chambers comprises using the substance flow or injecting a pressurized fluidum into any of the chambers.
Preferably, the method is used for an apparatus as described above for removing magnetizable particles in the substance.
In an embodiment, a method is provided for removing magnetizable particles from a substance, the method comprising the steps of
In an embodiment, the step of inducing flocculation comprises providing a second magnetic field applied in the flocculation chamber.
In an embodiment, the method further comprises the step of reducing the flow velocity of the substance prior to and/or during the step of forming flocs and during the step of separation in the magnetic separation chamber.
In an embodiment, the method further comprises the step of cleaning the magnetic separation chamber and/or the flocculation chamber.
In an embodiment, the step of cleaning any of the chambers comprises removing the respective magnets from the chamber.
In an embodiment, the step of cleaning of any of the chambers comprises using the substance flow or injecting a pressurized fluidum into the any of the chambers.
The apparatus 100 is a magnetic separator or filtration system comprising a magnetic separation or filter chamber 110 for filtering magnetizable particles and flocs from the substance, and a flocculation chamber 130, possibly comprised in a pre-magnetizing device 150, for inducing flocculation of the particles in the substance.
The magnetic separation chamber 110 comprises a first housing 112 that defines a first space 114 through which the substance can flow. The magnetic separation chamber further comprises a plurality of first magnets 116 of which a first magnetic field reaches into the first space 114. The first magnets 116 are each located within first holders 118 that have an interface 120 with the first space 114.
The flocculation chamber 130 comprises a second housing 134 that defines a second space 136 through which the substance can flow. In addition, the flocculation chamber 130 comprises a plurality of second magnets 138 of which second magnetic fields reach into the second space 136. The second magnets 138 are each located within second holders 140 that each have an interface 142 with the second space 136. The magnetic fields of the second magnets 138 causes the magnetizable parts in the substance to be attracted to each other, thereby undergoing flocculation and forming flocs.
The flocculation chamber 130 is in fluid connection with the magnetic separation chamber 110 through connection flanges 122 and 132, respectively, placing the magnetic separation chamber 110 and the flocculation chamber 130 adjacent to each other.
The magnetic separation chamber 110 is located downstream of and adjacent to the flocculation chamber 130. The flocculation of the magnetizable particles by means of pre-magnetization, results in magnetizable flocs. The magnetic field of the first magnets 116 causes the magnetizable flocs to be attracted towards the first magnets 116 thereby removing the flocs of magnetizable parts from the substance. The first space of the magnetic separation chamber defines a spatial volume which is greater than the spatial volume defined by the second space of the flocculation chamber, and which second space spatial volume is greater than the spatial volume of the conduit system. The spatial volume of a chamber defines the residence time of the substance in the chamber.
The second housing 134 of the flocculation chamber 130 is provided with an inlet part 144 that is connectable to a conduit system 106, see
The inlet part 144 widens out to the flocculation chamber 130 to decrease a flow rate of the substance flowing into the flocculation chamber. As such, a first part 146 of the inlet part 144 has a diameter similar to that of the conduit system 106, and a second part 148 of the inlet part 144 tapers out to a larger diameter similar to the diameter of the flocculation chamber 130. The outlet part 124 tapers away from the magnetic separation chamber 110 to a diameter similar to that of the conduit system 106. In this embodiment the inlet part 144 and the outlet part 124 are arranged on different sides (such as opposite) of the magnetic separation chamber.
The first holders 118 of the magnetic separation chamber 110 extend into the first space 114, such that a longitudinal direction of the first holders 118 is substantially perpendicular to a downstream direction Du directed from the flocculation chamber 130 towards the magnetic separation chamber 110. Each first holder 118 comprises a tube that is closed at one end that is located in the first space 114. The first magnets 116 have a rod-like shape. Each rod-like first magnet 116 extends into one first holder 118 with a releasable fit, i.e. an air gap between an internal wall of the first holder and the first magnet 116. As the first magnets extend into the first space, a direction of the first magnetic fields is substantially perpendicular to the downstream direction Du.
The second holders 140 of the flocculation chamber 130 extend into the second space 136, such that a longitudinal direction of the second holders 140 is substantially perpendicular to a downstream direction Du directed from the flocculation chamber 130 towards the magnetic separation chamber 110. Each second holder 140 comprises a tube that is closed at one end that is located in the first space 136. The tube may even extend from a first side of the flocculation chamber 130 to beyond a second opposite side of the flocculation chamber 130, as shown in
The second magnets 138 have a cross section that has a greater dimension in the downstream direction Du with respect to a dimension in a direction transverse to the downstream direction, i.e. the major dimension is directed in the downstream direction.
The first magnets 116 have a circular cross section. The cross section of the first holder is similar to that of the first magnets, however with a slightly larger diameter to allow for an air gap between the first holder 118 and the first magnet 116.
The magnetic separation chamber 110 further comprises a cleaning system 126 to clean the inside of the first housing 112. The cleaning system 126 may comprise, a sprinkling or spraying member to clean the outside of each tube by spraying a fluidum towards the first holders 118. Said sprinkling or spraying member may comprise an annular pipe provided with a plurality of sprinkling or spraying nozzles which can be fed with a fluid, such as a liquid or gas. The nozzles can be situated in the first space 114 in various ways. According to
The device 150 is connectable to the magnetic separation chamber 110 by means of connection flange 132. Further connection flange 128 can be used to connect the inlet part 144 to the flocculation chamber 130. The device 150 can be used for retrofitting an existing magnetic separation system or any other system, method, or technology for separation in need of a pre-magnetization treatment such as those involving hydro cyclone or multi cyclone technology.
Additionally, the second magnets 138 and the first magnets 116 have been removed from the second and first holders, respectively, by the first and second movement mechanism 102, 104, respectively. The movement mechanisms 102, 104 can be hydraulically actuated, but other forms of actuation may be used as well. For the apparatus of
Despite the removal of the magnets, some particles may nevertheless remain behind on the holder wall. In order to be able to remove these particles reliably, the sprinkling or spraying member for cleaning the outside of each tube is situated near the bottom end of each tube. The spraying member is part of the cleaning system and sprays a fluid (liquid or gas) towards the tubes to remove any particles left on the holder wall. The sprayed-off particles are then removed from the magnetic separation chamber 110 through the discharge 158.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017443 | Sep 2016 | NL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NL2017/050591 | 9/11/2017 | WO | 00 |
