Ball mills and methods for grinding materials

Abstract

The present disclosure relates to ball mills, ball mill bases, ball mill jars, and to methods for grinding materials. A ball mill comprises a ball mill housing comprising a rotatable base within the housing, the base being configured to eccentrically support a jar and to rotate the jar in a first direction around an axis perpendicular to the base. The base comprises a resilient flexible coupling for supporting the jar on the base.

Description

ANTONIJO LICITAR ET AL. DECEMBER 10, 2025P5385PC00BALL MILLS AND METHODS FOR GRINDING MATERIALS

[0001] The present application claims the benefit of European patent application n° EP24383354.8 filed on December 11th, 2024.TECHNICAL FIELD

[0002] The present disclosure relates to ball mills and methods for grinding materials, for example for producing nanoparticles. The present disclosure further relates to ball mills configured to receive and rotate at least one jar, and to rotatable bases used in such ball mills and methods.BACKGROUND

[0003] Nanoparticles generally have at least one of their dimensions, optionally all their dimensions, between 1 nm and 100 nm. As the surface area to volume ratio of the material becomes significant in the nanoscale, the properties of the nanoparticles may be different from the properties of larger particles. Nanoparticles are used in a wide range of fields, for example medicine, electronics, materials science and others.

[0004] Current methods of producing these materials often involve bottom-up processes or production methods that require the use of chemicals and high energy consumption. These processes may be time-consuming and expensive.

[0005] A known top-down approach involves a ball mill including grinding balls. The ball mill may reduce the size of the input material. Reducing particle size to a desired size or size range generally requires long grinding times as well as a lot of energy. Obtaining large amounts of particles of a desired size or in a desired size range may also be difficult. The grinding efficiency tends to be low.

[0006] The present disclosure aims at resolving, or at least reducing, one or more of the abovementioned disadvantages.SUMMARY

[0007] In an aspect of the present disclosure, a ball mill is provided. The ball mill comprises a housing, a base and a jar. The base is arranged within the housing and is configured to rotate in a first direction around an axis perpendicular to the base. The jar is eccentrically mounted on the base. The base and / or the jar comprises a resilient flexible coupling for supporting the jar on the base.

[0008] The ball mill comprises a base with an eccentrically arranged jar, i.e. the jar is offset from the axis of rotation of the base. Rotating the base rotates the jar. An input material of which the size is to be decreased may be introduced in the jar together with a plurality of grinding balls. The rotation of the base, and therefore of the jar with the grinding balls and the input material inside, may crush the input material.

[0009] The resilient flexible coupling between the base and the jar allows the jar to wobble. The ball mill may be configured to wobble the jar during operation of the ball mill. Accordingly, the collisions of the input material with the inner walls of the jar, the grinding balls inside the jar and with other input material may be increased. A size of the input material may be reduced to a desired size in less time in this manner. Also, more particles of a desired size or within a desired size range may be obtained.

[0010] The resilient coupling may specifically include one or more flexible elements, for example rubber, elastomeric materials or springs to provide cushioning and reduce the transmission of shock and vibration under load.

[0011] Wobbling of the jar may be achieved in several manners. In some examples, an inner lateral surface of the ball mill housing comprises at least one electromagnet. In these examples, an outer lateral surface of the jar comprises at least a magnetic or ferromagnetic portion, for example at least one permanent magnet. When the jar is arranged on the base, by switching the electromagnet(s) on and off, the jar may wobble. Mixing of the input material and the grinding balls may be increased by using the electromagnets and the permanent magnets. In other cases, the location of permanent magnets and electromagnets may be the other way around.

[0012] In further examples, the ball mill may further comprise a vibrating platform for supporting the jar. For example, the vibrating platform may be arranged on the resilient flexible coupling. In these or other examples, one or more oscillators may be attached to an outer lateral surface of the jar. A vibrating platform or an oscillator may comprise a motor which, when switched on, may move the vibrating platform or the oscillator in different directions, thereby also moving the jar.

[0013] In some examples, the ball mill may be configured to rotate with respect to the base and around an axis extending along a longitudinal direction of the jar. The two axes of rotation, i.e. the axis of rotation of the jar and the axis of rotation of the base, are parallel when the jar is operatively arranged within the ball mill housing. In some of these examples, the jar may be rotated in a second direction opposite to the first direction. A planetary ball mill may thus be provided. The base may be referred to as sun wheel. Rotation around a rotation axis of the jar and around a rotation axis of the base may increase the mixing of the materials and the grinding balls, improving a grinding efficiency.

[0014] The base may be a plate in some examples. The base, e.g. the baseplate, may be disc-shaped. The ball mill may comprise an actuator or drive such as a motor, e.g. an electric motor, for rotating the base. The ball mill may further comprise a gearbox between the drive and the base, specifically between the drive and a shaft connected to the base. Activating the drive may therefore rotate the base around an axis perpendicular to the base, i.e. around a vertical axis. In some examples, the ball mill may further comprise another drive or actuator, e.g. a motor, for rotating the jar around itself. Another gearbox may also be provided between this second drive and the jar. The drive(s) and the gearbox(es) may be arranged below the base.

[0015] In other examples, a gas-powered system, an electromagnetically powered system, a hydraulic system, a pneumatic system and others may be used for causing rotation of the base. In some examples, a flywheel may be connected to the base for reducing stress during operation.

[0016] In some examples, the ball mill may further comprise an input pulley arranged with a base shaft for rotating the base, an output pulley arranged with a shaft for rotating the jar (e.g. a shaft for rotating a bottom portion of the resilient flexible coupling or an intermediate element between the resilient flexible coupling and the shaft for rotating the jar), and a belt connecting the input pulley and the output pulley. In this manner, when the base shaft is rotated, the base is rotated and the belt is moved. The belt moves the output pulley and therefore the shaft for rotating the jar. The jar can therefore be rotated by rotating the base shaft. In these examples, a separated motor for rotating the jar along its longitudinal axis may be dispensed with. The shaft for rotating the jar may be secured to the base, e.g. to a bottom surface of the base, in some examples. In other examples, this shaft may be rotatably connected to the base shaft, or simply connected to a bottom inside wall of the ball mill housing.

[0017] The ball mill may further comprise a tensioning element for tensioning the belt. One or more tensioning elements, e.g. tensioning rollers, may for example be connected to the base, for example to a bottom of the base, or simply to a bottom inside wall of the ball millhousing. The tensioning roller(s) may help to keep a suitable belt tension. Laterally, e.g. horizontally, displacing the tensioning element varies the tension on the belt and thereby may cause the belt to move vertically. For example, horizontally moving the tensioning element may cause the belt to move upwards or downwards along the output pulley. The speed of rotation of the jar may therefore be modified.

[0018] The input pulley and the output pulley may have a shape of a truncated cone. A continuous variable transmission may be provided in this manner. The sliding of the belt along an outer surface of the cones may help to vary a rotational speed of the jar. As previously mentioned, this may be achieved by displacing the tensioning element.

[0019] In some examples, the base may comprise a slot along which the jar can move between a first position closer to a center of the base and a second position further away from the center of the base than the first position. The jar may therefore be arranged at a certain distance with respect to the center of the base and secured therein, for example before the ball mill starts to operate. The linear speed at which the jar is rotated may thus be regulated. Therefore, the linear speed of the jar may be adjusted to the input material to be milled, for example to a stiffer or softer material, to an initial size of the input material, etc.. The milling time may be reduced, and the grinding efficiency may be improved.

[0020] In some other examples, fixing a position of the jar in the slot before starting the ball mill operation may be dispensed with. In such examples, when the base starts to rotate, and therefore the jar starts to rotate, such rotation may cause the jar to move along the slot towards a suitable position corresponding to the speed of rotation. For example, if the speed of rotation of the base plate is relatively high, the jar may move radially outwards. In these examples, the tensioning element may adjust for a difference in distance between the jar and the central drive of the base plate.

[0021] The ball mill may further comprise a track below the slot to which the jar is slidably connected for moving the jar along the slot. For example, one or more rollers may slidably connect the jar and the track. The roller(s) may slide on or along an inside of the track, e.g. along a cavity inside the track. The track may for example be connected to the base, e.g. to a bottom surface thereof.

[0022] The slot may be curved. The slot may be C-shaped in some examples. A curved slot, e.g. a C-shaped slot, provides a longer trajectory between the ends of the slot than a straight slot. The position of the jar and its speed of rotation may be adjusted in a finer or more precise manner. The movement of the material to be grinded introduced in the jar may therefore be more precisely controlled as well.

[0023] The ball mill may further comprise a microwave emitter for heating at least a portion of the material inside the jar. The microwave emitter may be arranged with the housing of the ball mill in some examples, for example with a top portion thereof. Microwaves, i.e. electromagnetic radiation with wavelengths ranging from about 1 m to 1 mm, or equivalently with frequencies between 300 MHz and 300 GHz, may heat the input material. Heating with microwaves, e.g. from above the jar(s), may induce structural changes in the input material, for example small cracks due to thermal stress. The energy required for milling the heated, and thus weakened, material may therefore be lower than the energy required for milling the non-heated material. If the input material comprises two or more components or materials, a specific component or material may be heated, facilitating reducing its size. Weaking the input material in this manner may also reduce grinding time, as the material may break more easily.

[0024] A control unit of the ball mill may help to control the emission of microwaves. For example, the wavelength of the radiation and the time period during which it is emitted may be controlled in a precise manner.

[0025] The base of the ball mill may further be configured to eccentrically support one or more additional jars. These jars may be as the jar described herein (see below), e.g. cone- shaped and / or comprising a plurality of compartments. If the ball mill is configured to receive a single jar, then a counterweight may also be connected to the base for balancing the jar when rotating the base.

[0026] In some examples, a single belt and a single tensioning element may be sufficient to rotate all the jars inside the ball mill housing. In other examples, more than one belt and more than one tensioning element may be provided.

[0027] The ball mill may comprise one or more platforms or frames for receiving the jar(s), e.g. a cylindrical or claw-shaped frame. The frames may help to further secure the jars when rotating. The frames may be connected to the base. For example, a ball mill may comprise a base and a plurality of frames above the base onto or into which the jars can be operatively arranged. In a planetary ball mill, the base may be seen as the sun and the frames may be seen as the planets. A platform or frame may for example be provided on the corresponding resilient flexible coupling, such that the frame and the jar supported by the frame may wobble.

[0028] The ball mill may further comprise a controller or control unit. The controller may be configured to control, e.g. manage and coordinate, the operation of the ball mill. The controller may have one or more processors and one or more memories with instructions which may be executed by the one or more processors. The ball mill may further comprise a plurality of sensors which may be communicatively coupled, e.g. wirelessly, to the controller at least insome examples. Examples of sensors may be temperature sensors, humidity sensors, pressure sensors, rotational speed sensors and others. The measurements of the sensors may help to precisely control and adjust the operation of the ball mill in real time. The ball mill may include a control panel such as a screen communicatively connected to the controller. An operator may adjust some parameters with the control panel.

[0029] The ball mill may be used for dry grinding as well as for wet grinding. The input material may be provided in powder form. In some examples, a liquid may be introduced in the jar besides the grinding balls and the material to be grinded. The input material in powder form may be micron sized in some examples, e.g. of a few or tens or hundreds of microns. The solid material may also have other suitable sizes, e.g. of less than one micron or up to a few millimeters.

[0030] The ball mill may comprise one or more plasma torches. The plasma torches may be connected to the jar such that a material inside the jar may be heated and fused for providing sintered material. In some examples, a size of the input material is first reduced, and then a plasma torch heats the grinded material for sintering at least a portion of it.

[0031] Nanosized materials as well as materials of a bigger size, e.g. micron-sized materials, may be used as input in a sintering process. Slurries, dispersions and gas mixtures including solid material may also be used as inputs for the jar in the sintering process. The sintered material may be a nanosized material, but it may also have larger dimensions. The sintered material may include two or more different materials, e.g. two or more nano-sized or micron-sized materials.

[0032] Besides being configured for sintering, the ball mill may be configured for synthesizing a material. For example, two or more different materials may be introduced in the jar, collided and then bonded together due to some chemicals or gases that are also introduced into the jar.

[0033] The ball mill may be configured to generate hydrogen (H2) inside it. In some examples, hydrogen gas and (nano)particles may be simultaneously produced. Colliding oxidizable metallic material in the jar(s) may activate the material such that the produced nanoparticles are able to react with water molecules, in particular without adding a base such as potassium or sodium hydroxide (KOH and NaOH). Alkaline water, i.e. water in which there is an excess of hydroxide ions (OH-) over hydrogen ions (H+), may also (but does not need to be) be used. A metallic material herein may include both metals (iron (Fe)), aluminum (Al), calcium (Ca), magnesium (Mg), zinc (Zn)... ) and metalloids (e.g. silicon (Si)). The oxidizable metallic material may further comprise a non-metallic element or compound. The oxidizablemetallic material may comprise oxygen in some examples. For example, the oxidizable metallic material may be AI2O3, FeC>2 or MgO.

[0034] The reaction between a metal and water (any suitable type of water) may produce a hydroxide besides hydrogen gas. For example, for Al, Ca, Mg and Zn the following reactions may occur, respectively: 2AI + 6H2O -> 2AZ(OH)3+ 3H2, Mg + 2H2O -> Mg(0H)2+ H2, Ca + 2H2O Ca 0H)2+ H2and Zn + 2H2O Zn 0H)2+ H2. By colliding the metals, or other suitable oxidizable metallic materials, in presence of water, hydroxides may be obtained.

[0035] Additives may be added for improving the reaction between the oxidizable metallic material and the water. For example, if the oxidizable metallic material comprises silicon, graphene or activated carbon, this may help to improve the reaction between the material and the water. Such additives may also be included in the oxidizable metallic material. For example, the oxidizable metallic material may include nano-sized activated carbon or graphene. An oxidizable material may herein refer to a material which is capable of removing and capturing oxygen from a water molecule, such that hydrogen is produced in the process. Other additives that may be used are for example iron nanoparticles or nickel (Ni).

[0036] The use of nickel may help to weaken the bonds between the hydrogen and the oxygen of the water molecules by bonding to the hydrogen atoms of the water molecules. Nickel may therefore help to promote the reaction between the oxidizable material and the water molecules. Also, nickel may help to break the water molecules, the hydrogen atoms remaining attached to the nickel. Accordingly, hydrogen production may also be enhanced.

[0037] Nickel may be introduced in the jar(s), e.g. in powder form, in some examples. In other examples, strips or other suitable elements comprising nickel, e.g. made of nickel or being coated with nickel, may be attached to an outlet of the jar, such that the liquid (including at least water) with oxidizable material of smaller size after traveling through the jar may be passed and contacted with the nickel.

[0038] Therefore, an oxidizable material may be collided for obtaining nanoparticles which may react with water, for example seawater, without the need to use further chemical elements / compounds. Such a reaction may effectively produce hydrogen. For example, if silicon is used, the nanoparticles of silicon produced may undergo the following reaction: Si + 4H20 Si(0H)4+ 2H2. Hydrogen gas is therefore released. The silanol functional groups (Si- OH) of the orthosilicic acid (Si(OH)4) may then form siloxane bonds (Si-O-Si) and release water: 2SJ(OH)4OH^St - 0 - Si(0H2+ H2O. Subsequently, the released water molecules may react with the silicon nanoparticles which have not reacted yet, sustaining theproduction of hydrogen gas until the silicon nanoparticles have been consumed: 4H2O + Si Si 0H)4+ 2H2.

[0039] In some examples, the following reaction may occur inside a jar due to the high temperature and high pressure conditions: Si + 2H2O -> SiO2+ 2H2.

[0040] The chemical reactions above may cause the pH to decrease and a decrease in pH can increase the dynamics of the reaction. For example, decreasing a pH below 5 may help to speed up the process as well as to increase the reactivity of the Si nanoparticles. However, this will depend on which additive(s) and in which amount are added (if added at all). It may also be possible that the pH increases in some examples. In some examples, an acidic solution, e.g. comprising orthosilicic acid (Si(OH)4), may be added to accelerate the process for generating hydrogen gas.

[0041] Besides seawater, water such as tap water, deionized water, extra pure water, grey water, waste water, contaminated water, sewage water, water comprising oil or other types of water may be used.

[0042] In some examples, hydrogen may be produced in a separator system, for example in a centrifugal separator connected to the jar, see below. The hydrogen may be collected from the top of the centrifugal separator and a remaining liquid may be collected from the bottom of the centrifugal separator. Hydrogen may also be produced in, and collected from, the jar(s) in some examples. For example, a tube for extracting hydrogen gas may be coupled to a lid of a jar. A suitable tube clamp or tube holder may be used to secure and stabilize the tube, allowing it to remain connected to the jar while the jar is in motion. The tube may also cross the housing of the ball mill in some examples. The tube may lead to a chamber in which the hydrogen may be stored.

[0043] Although not necessary, a hydroxide compound such as KOH or NaOH may be used to trigger or initiate hydrogen production. This may accelerate the (initiation of the) process, as the reaction between water and the oxidizable metallic nanoparticles will start quicker. As KOH or NaOH may only be used to cause the reaction to initiate, and not to keep the reaction ongoing, a small amount of KOH or NaOH may be sufficient.

[0044] It should also be noted that nanoparticles suitable for producing hydrogen with the ball mill described herein may also be used outside the ball mill. For example, the nanoparticles may be mixed with water, e.g. seawater, for producing hydrogen in a suitable container outside the ball mill. For example, a reactor may be used for producing the hydrogen.

[0045] The ball mill described herein may also be used for other purposes and / for generating other gases besides hydrogen. For example, a gas generated during the processmay be or may include syngas, methane (CH4), carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), hydrocarbon gas, noble gas and others.

[0046] For example, jar(s) and the ball mill may be configured to produce syngas from coal and water, emulating a water-gas shift reaction. In some examples, a gas such as CO may be added to the water for producing a water-gas shift reaction in which CO reacts with H2O for producing CO2 and H2. Methane (CH4) and other carbon-based fuels may also be introduced in the jar(s). For example, CH4 may be added to the water for producing CO2 and H2. In other examples, CO2 may be used, together with water, to produce CO. Syngas may efficiently be generated. Catalysts such as calcium (Ca) and copper-silicon (CuSi) may help to enhance the efficiency of producing CO from CO2.

[0047] The ball mill may therefore be used to generate gases such as syngas or hydrogen in which the nanoparticles obtained may be used subsequently for other applications.

[0048] The ball mill described herein may also be used for liquefying coal by hydrothermal liquefaction (HTL). Coal and water may therefore be added to the jar(s) of the ball mill. Therein, the coals and the water may be subjected to high pressure and high temperature. This may break the coal into simpler organic compounds, and the solid coal and water may form a coal slurry. The coal may therefore be liquefied. Depending on which additional elements are added with the coal, other products such as biodiesel, e.g. including methanol or ethanol, may be obtained.

[0049] As oils and bio oils, e.g. which have already been used in other processes, comprise a significant amount of carbon and hydrogen, adding them with the coil may help to increase the yield of the corresponding product. Catalysts, for example biodiesel or methanol, may help to expedite the liquefaction process and promote the conversion of coal other additional elements into liquid products.

[0050] Alcohol sources such as methanol or ethanol may be included in the jar(s) with the coal. The high temperature and high pressure inside the jar(s) may promote the obtention of liquid fuels including methanol or ethanol.

[0051] After HTL, the obtained product, e.g. a slurry, may be refined. Separation techniques, for example distillation, may be used to purify the obtained product.

[0052] In another aspect of the disclosure, a method for grinding material is provided. The method may use the ball mill of the previous aspect. The method comprises introducing the material to be grinded in a jar. The method further comprises introducing a plurality of grinding balls in the jar. The method further comprises reducing a size of the material by rotating the jar (around a rotation axis of the base of the ball mill) and by wobbling the jar.

[0053] Therefore, the material whose size is to be reduced and the grinding balls are introduced in the jar. With the jar closed and operatively connected to the base, and with the ball mill closed and secured, the base, and therefore the eccentric jar, are rotated. The rotation causes the input material and the grinding balls to move. The jar is wobbled. The size of the input material is reduced.

[0054] The jar may be wobbled in different manners. For example, one or more electromagnets arranged at an inner lateral surface of the ball mill housing may be switched on and off. The interaction between the magnetic field of the electromagnet when switched on and for example one or more permanent magnets of the jar may wobble the jar.

[0055] The jar may additionally or alternatively be arranged on an oscillator such as a vibrating plate. One or more oscillator devices may also be attached to an outer surface of the jar.

[0056] The input material may be micron sized material or even material up to a few millimeters in size. Therefore, when the ball mill is operated and the jar is wobbled, the size of the input material may be reduced by colliding with itself, by colliding with the inner walls of the jar, and by colliding with the grinding balls. In this manner, a more homogeneous size distribution may be obtained, and desired size ranges may be achieved faster.

[0057] Rotating the base may comprise varying a speed of rotation, for example in the first direction. Regulating the speed of rotation in the first direction may help to adjust the grinding process. For example, a height at which the grinding balls and the input material move may be regulated by increasing or decreasing the rotational speed. If the jar is also rotated around itself, for example in a second direction opposite to the first direction, the speed of rotation in the second direction may also be varied.

[0058] For example, if an input pulley and an output pulley connected by a belt are used, e.g. cone-shaped pulleys, the belt may be slid along the outer surface of the output pulley (and / or the input pulley) for adjusting the speed of rotation of the jar around itself. In these examples, the base and the jar generally rotate in the same direction.

[0059] The method may further comprise connecting the jar to a rotatable base, and rotating the rotatable base. In these examples, the method may further comprise mounting the jar on the rotatable base, which may comprise arranging the jar at a specific position along a slot in the base. I.e., if the ball mill comprises a slot, the jar, e.g. with the material to be grinded and the plurality of grinding balls, may be arranged (and optionally fixed) at a specific position along the slot. For example, an intermediate element or a bottom portion of the resilient flexible coupling may be slid along the slot and locked at a desired position. The step of fixing / lockingthe jar along the slot before the base is started to be rotated may be performed in some examples and omitted in other examples.

[0060] The grinding balls may comprise an outer hollow ball including through holes and an inner ball inside the outer hollow ball. Due to the holes of the outer hollow balls, the input material enters these balls. The input material may be further milled, and efficiency of the process may increase. Also, homogeneity in size of the milled material may increase. In addition, such grinding balls may be more durable with respect to wear and tear than usual solid balls.

[0061] The jar may have a shape of a truncated cone. The cone may taper towards the end which is to be connected to the supporting base of the ball mill, specifically downwards. A conical shape may create a gradient in grinding intensity, the grinding intensity increasing towards the narrowest end of the jar. A pressure exerted by the grinding balls inside the jar may increase towards the narrowest end as the space available decreases. Also, the rotation of the base may cause the grinding balls and the material inside the jar to move radially outwards and also upwards, and grinding balls of different sizes and weights may end up moving at different heights of the jar. For example, larger grinding balls may rotate at a greater height than smaller grinding balls with respect to the bottom of the jar or the supporting base. The material may thus collide with the grinding balls at different heights of the jar, increasing the number of collisions.

[0062] In other examples, the jar may have other shapes, e.g. a shape of a cylinder.

[0063] The jar may comprise one or more dividers dividing an inside of the jar into successive interconnected compartments, each compartment configured to receive a plurality of griding balls. For example, the jar may comprise one or more dividers with through holes for dividing the inside of the jar into two or more compartments. The dividers may be horizontal, i.e. parallel with respect to bottom of the jar. A divider may for example be a plate with a plurality of through holes, e.g. a perforated plate or sieve.

[0064] Having a plurality of compartments may help to separate the input material by sizes and collide it separately. For example, input material with particles having larger dimensions will tend to remain at a top portion of the jar, whereas material with particles of smaller dimensions may fall through a perforated plate to a lower portion of the jar. When the base, and therefore the jar, is rotated, the input material may be crushed at their own compartments depending on the dimensions of the particles.

[0065] In some examples, the jar may comprise at least two dividers, the dividers including through holes for interconnecting the compartments. A size of the through holes may varybetween the dividers, and the size of the through holes may decrease towards the base supporting the jar. I.e., a size of the through holes of an upper divider may be larger than a size of the through holes of a divider below the upper divider, and so on. This may be applicable for successive dividers from a top divider to a bottom divider. Therefore, once the input material of a certain compartment has been crushed to a size where it can go through the holes of the divider, the material may reach a lower compartment. The size of the material may be further reduced in the lower compartment. A higher homogeneity in size may be achieved in this way in the separate compartments. Different sizes of material may be extracted from the different compartments as desired.

[0066] In some examples, the jar may comprise a ceramic material. Thejar may for example be made of a ceramic material. A ceramic coating, at least to the inner surface of the jar, may be provided in other examples. Using a ceramic material for the jar can help to suitably mill material which may show magnetic effects. If the jar comprises one or more dividers, the divider(s) may comprise, e.g. be made of, a ceramic material. A lid of the jar may comprise, e.g. be made of glass. A lid may be provided separate from the remainder of the jar or may be provided connected to the remainder of the jar. For example, a jar may comprise a jar body and a lid rotatably, e.g. hingedly, connected to the jar body.

[0067] The atmosphere inside the jar may be suitably controlled. For example, the jar may include vacuum-sealing capabilities. Air and other gases may be removed from an inside of the jar. Also, inert gases such as argon or nitrogen may be introduced into the jar to create a controlled atmosphere. Inert gases may help to prevent oxidation or contamination of the input materials during milling.

[0068] A jar may comprise a lid configured to this end. For example, a tube for removing air and / or for providing an inert gas may be securely connected to a lid inlet (or outlet) by a vacuum fitting or a gas fitting. The tube may be flexible. An atmosphere within the jar may therefore be conditioned before starting to rotate the jar. The ball mill may further comprise a system for generating an under pressure or “vacuum”. A vacuum may herein be regarded as a significantly lower pressure than the pressure in the jar. The system may for example include a vacuum pump, dedicated tubing and valves for generating an under pressure or vacuum. The ball mill may additionally or alternatively comprise a system for introducing gases such as inert gases in the jar. This system may comprise dedicated tubing and valves.

[0069] In some examples, one or more gas sensors may be provided. The sensors may be arranged within the jar or near the jar. The concentration of gases present, for example oxygen, nitrogen or argon, may be detected. A control unit, accessible for example from an outside ofthe ball mill, may process the data obtained from the gas sensors. Gas concentration may therefore be monitored in real time.

[0070] Pressure and / or temperature inside the jar may also be monitored with suitable pressure sensors and temperature sensors.

[0071] A size of the grinding balls, e.g. of usual solid balls or e.g. of both the outer hollow balls and the inner balls, may decrease from a top compartment to a lower, e.g. bottom, compartment when the grinding balls are arranged within the jar. Decreasing a size of the grinding balls may help to increase a number of collisions between the input material and the grinding balls, thereby increasing the efficiency and the size homogeneity of the crushing process. Also, a number of grinding balls may increase from a top compartment to a bottom compartment. This may also help to increase a number of collisions of the input material and the grinding balls.

[0072] The inner balls, if present, may be solid in some examples. I.e., they may lack through holes and may not be hollow. The weight of the inner solid balls may be adjusted to the input material to be milled. For example, heavier inner balls may be used for milling harder or more ductile materials, whereas lighter inner balls may be used for milling softer or more brittle materials. Also, heavier inner balls may exert more force against an input material but, due to their weight, they may move slower within the outer hollow balls. Adjusting the weight of the inner balls may help to optimize efficiency by balancing the intensity and the frequency of the impacts.

[0073] In other examples, the inner balls may comprise a plurality of through holes. I.e., the input material may also enter the inner balls. Regardless of whether the inner balls are solid or not, the grinding balls may further comprise one or more additional middle balls between the outer balls and the inner balls, the additional middle balls comprising a plurality of through holes. Providing one or more middle balls may increase the collisions of the input material. A size of the through holes in the grinding balls may decrease radially inwards. I.e., the outer hollow ball may have bigger through holes than the next hollow ball and so on.

[0074] The outer hollow balls (and the middle hollow balls if present) may comprise two portions which may be removably attached. For example, a threaded connection or a bayonet connection may join the two portions. A suitable inner ball may be introduced inside the outer hollow ball.

[0075] The grinding balls, e.g. usual solid balls or e.g. the outer hollow ball and / or the inner ball, may be made of ferromagnetic material. The ferromagnetic material may be used for monitoring the trajectory of the grinding balls inside the jar. A suitable magnet sensor may bearranged in the jar. Knowing the trajectory of the grinding balls may help to adjust the milling process in real time. For example, the speed of rotation of the base may be increased or may be decreased. In other examples, the grinding balls may comprise magnets.

[0076] Reducing the size of the material may comprise obtaining nanoparticles. The nanoparticles (or in general the material of reduced size) may be removed from the jar. For example, the jar may be opened and the grinded material may be removed. In some examples, a collector system may be provided in the ball mill and around the jar, specifically around a bottom portion of the jar. The bottom portion of the jar, e.g. enclosing a bottom compartment, may comprise one or more outlets through which the grinded material may be removed.

[0077] The collection system may in some examples include one or more glove boxes, i.e. hermetically sealed enclosures for ensuring stability, providing a controlled environment for the grinded material and avoiding contamination.

[0078] If the bottom portion of the jar comprises a plurality of through holes, for example if the form of a perforated bottom portion, the collection system may be secured around the bottom portion such that the grinded material may advance to the collection system through the plurality of through holes during operation of the ball mill.

[0079] In other examples, a separator system may be provided in the ball mill for extracting the material from the jar, for example after the ball mill has been stopped. The separator system may be connected to an outlet of the bottom portion of the jar. Depending on whether dry or wet grinding is performed, the separator system may e.g. be a cyclonic separator or a centrifugal separator. In some of these examples, the separator system may be configured to generate an under pressure for removing the material from the jar. Other separator systems such as a system including gravity separation or a system including electro potential separation (using e.g. static electricity) may also be used.

[0080] In some examples, a collection system, which may comprise one or more valves, may be connected to the outlet of the separator system. The grinded material may therefore be collected and packed.

[0081] If the ball mill is used to generate hydrogen gas, water, optionally seawater, may be added to the jar(s) and / or to a separator system such as a centrifugal separator in some examples. The input material may comprise an oxidizable metallic material. The method may further comprise generating hydrogen (gas) from the produced nanoparticles, for example in the jar(s) of the ball mill or in the centrifugal separator connected to the jar(s). Nanoparticles from an oxidizable metallic material may react with surrounding water for producing hydrogen.

[0082] Particular aspects, examples and elements of aspects or examples disclosed herein can be combined together in any number and order to form new aspects and examples that form part of this disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 schematically illustrates a cross-sectional view of an example of a ball mill with a jar arranged therein.

[0084] Figure 2 schematically illustrates a cross-sectional view of a base with ajar arranged thereon and two pulleys connected by a belt for rotating the jar around itself.

[0085] Figure 3 schematically illustrates a top view of an example of a base of a ball mill with two slots.

[0086] Figure 4 schematically illustrates a cross-sectional of an example of a jar comprising a plurality of compartments and a plurality of grinding balls inside.

[0087] Figure 5 schematically illustrates a cross-sectional view of another example of a jar comprising a collection system arranged with the jar.

[0088] Figure 6 illustrates a flowchart of a method for grinding material with a ball mill system according to the disclosure.DETAILED DESCRIPTION OF EXAMPLES

[0089] Reference will now be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0090] In an aspect of the disclosure, a ball mill is provided. The ball mill comprises a housing, a base and a jar. The base is arranged within the housing and is configured to rotate in a first direction around an axis perpendicular to the base. The jar is eccentrically mounted on (i.e. operatively connected to) the base. The base and / or the jar comprises a resilient flexible coupling for supporting the jar on the base.

[0091] When the jar including the material to be grinded and the plurality of grinding balls is operatively connected to the base of the ball mill, the base may be rotated and the material may be grinded. The resilient flexible coupling may enable the jar to wobble, e.g. to deviate from a vertical direction in a repeated manner. Wobbling the jar may increase a number of collisions of the material inside the jar. This may decrease a time required to reduce the input material to a desired size and to obtain more particles of a desired size or within a size range.

[0092] Figure 1 schematically illustrates a cross-sectional view of an example of a ball mill 1 with a jar 2 arranged therein. The ball mill 1 comprises a ball mill housing 3. The ball mill housing 3 encloses the internal components of the ball mill, such as one or more jars 2 (when arranged in the ball mill), the base 5, which may be a baseplate, drives 6, e.g. motors, etc. The housing 3 protects the elements inside from external elements like dust or other contamination. The housing 3 provides structural support to the internal components of the ball mill, maintaining stability during operation.

[0093] In examples, a jar 2 may have a capacity up to 15 or 20 liters or more. A jar 2 may be able to process up to 1 kg of input material or more.

[0094] The ball mill 1 comprises a base 5, for example a baseplate. This base is rotatable, specifically around a vertical axis 7. When one or more jars are operatively connected to the base 5, rotating the base 5 rotates the jars. The jars are laterally, e.g. radially, offset from the center of the base 5. The ball mill 1 comprises a drive 6 such as an electric motor and a gearbox 8 below the base 5 for rotating the base 5.

[0095] The motor 6 may be an AC motor, a brushless DC electric motor, or in general any suitable motor for rotating a shaft and therefore the base 5. Other suitable drives or actuators for rotating the base at high speed may alternatively be provided.

[0096] In this example, the jar 2, e.g. a body of the jar, has a shape of a truncated cone. The jar may comprise a body or receptacle 4 for receiving the grinding balls and the material to be milled, and a lid 9. The lid 9 may be provided separately from the receptacle 4 in some examples. The lid 9 may be flat or may be curved, e.g. convex. The body or receptable 4 may comprise, e.g. be made of, a ceramic material. The lid 9 may be made of glass. In other examples, the jar 2 may for example may have a shape of a cylinder.

[0097] In this example, the ball mill 1 comprises a resilient flexible coupling 15 for supporting the jar 2 on the base 5. The resilient coupling 15 may include flexible elements such as springs and / or elastomeric materials such as rubber. An inner lateral surface of the ball mill housing 3 may comprise at least one electromagnet 17. An outer lateral surface of the jar may further comprise at least one permanent magnet 16 (or the jar may have a magnetic portion). Forexample, a plurality of electromagnets may be arranged on the inner lateral surface of the ball mill housing 3 in columns, and a plurality of electromagnets may be arranged on the outer lateral surface of the jar 2 in columns. When the electromagnets are switched on and off, the jar 2 may wobble due to the presence of the electromagnets and the permanent magnets. A wobbling of the jar has been depicted in figure 2 with a double headed arrow above the jar.

[0098] In further examples, the jar 2 may have a suitable first connector for connecting to the resilient coupling. The resilient coupling in this case has a suitable connector for connecting with the first connector of the jar. The first and second connectors may be of any suitable type, including e.g. a bayonet connector, male and female connectors, a snap-on fitting, or a threaded connection. The second connector may form an integral part of the resilient flexible coupling, but could also be arranged on top of the resilient flexible coupling. The second connector, e.g. a platform with a suitable shape, may be vibrated to wobble the jar. Still in this or other examples, one or more oscillators may be arranged on a lateral outer surface of the jar.

[0099] In yet further examples, the jar may be retained on the base by e.g. claws or grippers retaining the top or an upper part of the jar on the base. For example, the jar may be on, or within, a claw-shaped frame. Such jaws or grippers may wobble with respect to the base due to the resilient flexible coupling.

[0100] The ball mill 1 may be configured to rotate the jar 2 around an axis extending along a longitudinal direction of the jar 2 and with respect to the base 5. Figure 2 schematically illustrates a lateral view of a base 5 with a jar 2 arranged thereon and two pulleys 26, 27 connected by a belt 28 for rotating the jar 2 around itself. Two axes of rotation are seen in this figure: the axis 7 around which the base 5 rotates and the axis 29 around with the jar 2 rotates.

[0101] The ball mill may further comprise an input pulley 26 arranged with a base shaft for rotating the base 5, an output pulley 27 arranged with a shaft for rotating the jar 2 around its longitudinal axis 29, and a belt 28 connecting the input pulley 26 and the output pulley 27.

[0102] In this manner, an actuator, e.g. a motor, may rotate the shaft for rotating the base 5, and therefore the base 5 and the input pulley 16. The belt 28 may transmit the movement to the output pulley 2, and this may rotate the shaft connected to for example a portion of the resilient flexible coupling which supports the jar 2. This portion of the resilient flexible coupling is rotatably mounted on the base in this case. Alternatively, one or more intermediate elements may be arranged between the shaft of the output pulley 27 and the resilient flexible coupling. The shaft of the output pulley 27, the one or more intermediate elements, the resilient flexible coupling and the jar 2 are therefore rotated.

[0103] In the illustrated examples, the base 5 and the jar2 are rotated in the same direction.

[0104] The ball mill may further comprise a tensioning element 30 for tensioning the belt 28. In some examples, the belt 28 may surround the output pulley 27, the input pulley 26 and the tensioning element 30, see figure 2. The tensioning element 30 may be rotatable around its own axis of rotation, e.g. an axis parallel to the axis of rotation 7 of the base 5. The tensioning element 30 may be movable, e.g. slidable or pivotable, for regulating the tension and height of the belt 28. In the example of figure 2, the tensioning element 30 is slidable. For example, horizontally displacing the tensioning element 30 with respect to a bottom inner wall of the ball mill housing may cause the belt 28 to vertically move along the output pulley 27.

[0105] The input pulley 26 and the output pulley 27 may have a shape of a truncated cone. In some examples, the output pulley 27 may taper upwards and the input pulley 26 may taper downwards. In other examples, a longitudinal axis of the pulleys 26, 27 may be arranged horizontally instead of vertically.

[0106] In some examples, the base 5 may comprise a slot 31 along which the jar 2 can move between a first position closer to a center of the base 5 and a second position further away from the center of the base 5 than the first position, see figure 3. Figure 3 schematically illustrates a top view of an example of a base 5 of a ball mill with two slots 31 . The base 5 may have none, one or more slots, e.g. four or six slots, in other examples.

[0107] A slot 31 enables to position the jar 2 at a certain distance from the center of the base 5. The linear speed of rotation of the jar 2 may therefore be adjusted. The slot 31 may be curved, e.g. C-shaped.

[0108] The ball mill may include a track below the slot 31 to which the jar 2 may slidably be connected for moving the jar 2 along the slot 31. For example, an intermediate element or a bottom portion of the resilient flexible coupling may be connected to a track through a shaft and at least one roller. The intermediate element of the bottom portion of the resilient flexible coupling may therefore be moved along the track, and therefore along the slot 31. In some examples, the jar 2 may be secured, i.e. fixed, such that it does not move along the slot 31 when the base 5 rotates. In other examples, this step may be omitted.

[0109] The jar 2 may be connected to the center of the of the base 5 via a biasing element. For example, the shaft for rotating the jar 2 and the shaft for rotating the base 5 may be coupled via a spring or another suitable biasing element. When the jar is not fixed in the slot 31 , but rather allowed to move along the slot based on the rotational speed of the base 5, the biasing element may cause the jar 2 to move towards the center of the base 5 when the base 5 reduces its speed of rotation.

[0110] If the ball mill 1 comprises one or more other jars, each jar may be connected to the center of the base 5 with via a biasing element. Alternatively, two or more jars may be connected via one or more biasing elements. For example, a biasing element may connect two jars such that they move towards the center of the base 5 when the base decelerates.

[0111] The ball mill 1 may further comprise a microwave emitter 18 for heating at least a portion of the material inside the jar 2, see figure 1. The microwave emitter 18 may be arranged on a top portion of the ball mill 1. The material inside the jar may be heated up by the microwaves emitted by the microwave emitter 18. This may facilitate breaking the material down.

[0112] Figure 4 schematically illustrates a cross-sectional of an example of a jar 2 comprising a plurality of compartments 10 and a plurality of grinding balls 11 inside. In this example, the jar 2 comprises five compartments. The jar 2 comprises a plurality of dividers 14 dividing an inside of the jar 2 into successive interconnected compartments 10. Grinding balls are arranged in each compartment 10.

[0113] The dividers 14 include through holes for interconnecting the compartments 10. A divider 4 may for example be a perforated plate or a mesh-like plate. The size of the through holes of the dividers 4 decreases from the top divider to the bottom divider. The material to be grinded may be placed in the top compartment. When a portion of the material is small enough, it may pass through the holes of the divider 4 below it and reach the next compartment 10 and so on. The speed of rotation of the base 5 may for example be decreased to allow the smaller particles to travel to the next compartment if gravity is not sufficient. The dividers in this case work as sieves.

[0114] In some examples, the grinding balls 11 mat comprise an outer hollow ball with through holes 12 and an inner ball 13. In this example, the inner balls are solid, i.e. they do not comprise through holes and are not hollow. In other examples, the inner balls may comprise through holes. In any of these examples, the grinding balls may comprise one or more middle hollow balls with through holes between the inner ball 13 and the outer hollow ball 12.

[0115] The outer hollow balls 12 may comprise two portions which may be removably attached. For example, a threaded connection or a bayonet connection may join the two portions. In this manner, an outer hollow ball may be used with different inner balls 13, for example inner balls of different sizes or weights. In general, different outer hollow balls may be combined with different inner balls, enabling an optimized milling process.

[0116] The grinding balls 11 , or at least a portion therefore, e.g. the outer hollow balls 12, may be made of ferromagnetic material. In some cases, the grinding balls 11 may comprisemagnets, for example permanent magnets. These ferromagnetic material or magnets may help to monitor the trajectory of the grinding balls 11 inside the jar 2. This information may enable the adjustment the milling process in real time. For example, the speed of rotation of the base may be increased or may be decreased in response to the measurements.

[0117] Figure 5 schematically illustrates a cross-sectional view of another example of a jar 2 comprising a collection system 19 arranged with the jar 2. Specifically, the collection system 19 laterally surrounds a bottom portion of the jar 2. A seal may be provided between the collection system 19 and the lateral outer surface of the jar for preventing leakage of the grinded material.

[0118] A bottom portion of the jar, e.g. a bottom lateral portion of the jar, may comprise a plurality of through holes. The example of this figure includes five dividers interconnecting six compartments inside the jar. The lateral portion of the jar delimiting the bottom compartment comprises the plurality of through holes. When the material has been milled to such an extent that it has reached the bottom compartment and is sufficiently small to cross the holes of the lateral portion of the jar, the milled material may reach the collection system 19 due to rotation of the base 5 and the jar 2.

[0119] In other examples, a separator system such as a cyclonic separator or a centrifugal separator may be provided between the jar 2 and the collection system 19. The rotation of the base 5 may be stopped, the separator system may be connected to the jar 2, and the collection system 19 may be connected to the separator system. The separator system may be connected to the jar 2 at several heights of the jar. I.e., it may be connected to the bottom compartment, but also to upper compartments depending on the desired size of the milled material. The separator system may be connected to a suitable outlet of the jar 2. The jar 2 may comprise dedicated outlets through which the milled material may be removed in some examples.

[0120] The ball mill 1 may further comprise one or more additional jars, the base further being configured to eccentrically support the additional jars. In this manner, material to be milled may be introduced in more than one jar. The jars may be rotated jointly in the first direction by rotating the base 5. The features and explanations provided with respect to the (first) jar may be applicable to the additional jars too.

[0121] The ball mill 1 may further comprise a plurality of sensors, for example temperature sensors, humidity sensors, pressure sensors and rotational speed sensors. The sensors may be communicatively connected to a control unit 25 such as a control panel, see figure 1. Thecontrol unit 25 may control the operation of the ball mill 1 during the milling process based on real-time data obtained by the sensors.

[0122] The ball mill system may be used to in dry grinding and in wet grinding. The ball mill may also be used for sintering material, e.g. after having milled the input material. The input material may comprise more than one material, component or element. The ball mill 1 may also be used for producing hydrogen gas. Water, e.g. seawater, may be added to the jar 2. The input material may be an oxidizable metallic material.

[0123] Figure 6 illustrates a flowchart of a method 20 for grinding material with a ball mill system according to the disclosure. The method 20 comprises, at blocks 21 and 22, introducing the material to be grinded in the jar 2 and introducing a plurality of grinding balls in the jar 2. The jar 2 may be outside the ball mill 1 or inside the ball mill 1 when it is filled. The material may be provided in powder form. In some examples, a roto valve connected to a storage container may be used for precisely controlling the amount of input material introduced in the jar 2.

[0124] When the jar 2 has been filled and closed, it may be arranged inside the ball mill 1 . Specifically, the jar 2 may be secured at an eccentric position on the base 5 of the ball mill 1. For example, the method may further comprise connecting the jar 2 to a rotatable base 5. For example, the jar 2 may be secured at a position along a slot 31 , see figure 3. In other examples, securing the jar 2 at a position along a slot 31 may be omitted. In some examples, the jar 2 may be secured to a top portion of the resilient coupling or to a platform or frame, e.g. a clawshaped frame. In any of these examples, a flexible coupling 15 is provided between the jar 2 and the (main) base 5, for example between the platform and the baseplate 5.

[0125] The input material may be introduced first, or the grinding balls 11 may be introduced first. If the jar 2 comprises two or more compartments 10, the grinding balls may be introduced first, such that each compartment 10 includes a plurality of grinding balls. All the compartments 10 may be provided with grinding balls 11 including outer balls with through holes and inner balls within the outer balls. In other examples, at least one compartment, optionally all the compartments, may include, for example, solid grinding balls only. The input material may be introduced from the top of the jar 2. All the input material, or the majority of the input material, may remain in the top compartment. The compartments 10 reached by the input material will depend on the size of the material and on the size of the through holes of the dividers 14.

[0126] Removable dividers 14 may be positioned while introducing the grinding balls. For example, first grinding balls may be introduced, and then a first divider may be positioned above them. Next, second grinding balls may be positioned on top of the first divider, and asecond divider may be positioned above them, and so on. In other examples, the jar 2 may comprise sealable inlets through which the grinding balls may be introduced. The dividers 14 may be fixed, i.e. not removable, in these examples.

[0127] In general, the dimensions and weight of the grinding balls 11 , as well as the number of grinding balls and compartments 10, may be adapted to the material and to the amount of the material to be milled.

[0128] The atmosphere inside the jar 2 may be conditioned, for example before the rotation of the base 5 has started. Vacuum and / or gas fittings in the jar 2, e.g. on a lid thereof, may allow to set the pressure and the atmosphere inside the jar. A fluid such as nitrogen (gas) may help to maintain a controlled level of oxygen during the grinding process. A fluid such as argon (gas) may help to create a controlled environment for certain processing conditions. Other suitable fluids may be used. A vacuum pump may generate a vacuum inside the jar 2. In some examples, vacuum may be performed in the jar 2, and then a fluid such as nitrogen or argon may be introduced in the jar 2.

[0129] Method 20 further comprises, at block 23, reducing a size of the material by rotating the jar 2 and by wobbling the jar 2. For example, the ball mill 1 may be closed, e.g. with a top lid, see figure 1 , and a drive 6 such as an electric motor may rotate a shaft to which the base 5 is connected, and may therefore rotate the base 5. Wobbling the jar 2 helps to mix the input material and to increase a number of collisions of the input material.

[0130] If grinding balls 11 with outer hollow balls 12 with through holes and inner balls 13 are present, at least a portion of the material may go through the holes of the outer hollow balls. This may help to reduce a grinding time as well as to increase a homogeneity in size of the grinding material.

[0131] In some examples, electromagnets 17 and permanent magnets 16 may be used to wobble the jar 2, see figure 1. As previously explained, the jar may be wobbled in other manners. For example, the jar 3 may comprise a magnetic portion, and / or one or more oscillators may be used.

[0132] Rotating the base 5 may comprise varying a speed of rotation, for example in the first direction. For example, a gearbox 8, see figure 1 , may be used to control a rotational speed in the first direction. If the jar 2 is also rotated about itself, this speed of rotation may additionally or alternatively be varied. Varying the speed may help to control the milling process, e.g. the time required for milling and the particle size achieved. It also may help to move the material between compartments 10 if they are present in the jar 2.

[0133] If the jar 2 includes a plurality of compartments 10, see e.g. figures 4 and 5, a size of the grinding balls 11 may decrease from a top compartment to a lower compartment, e.g. a bottom compartment. The milling may be more intense in the lower compartments in this manner. This may help to increase the efficiency of the milling process as well as to achieve a more homogeneous size distribution of the milled material.

[0134] As previously mentioned, one more additional jars may be filled and operatively connected to the base 5 for being rotated too. In some of these examples, a single belt 28 may connect all the jars, such that rotating the base 5 may rotate all the jars inside the housing of the ball mill. In other examples, more than one belt and more than one tensioning element may be provided. For example, one belt may connect the base 5 and two jars, and another belt may connect the base 5 and two other jars. Each belt 28 may be regulated with its own tensioning element 30. In examples where a single jar 2 is provided inside the ball mill 1 , a counterweight may be provided for balancing the jar 2.

[0135] Reducing the size of the material may comprise obtaining nanoparticles in some examples. Regardless particles in the nanoscale or bigger particles are obtained, they may be collected from the jar 2. For example, a separator system, e.g. a cyclonic separator or a centrifugal separator, may be connected to an outlet of the jar 2 after the base 5 has been stopped and the jar 2 is no longer rotating. An under pressure or “vacuum” may be generated for moving the grinded material to the separator system. The separator system (or other system in other examples) may be configured to create an under pressure in the outlet of the jar 2. The separator system may be configured to separate material by size or density in some examples. The system may separate the solid material in two or more groups according e.g. to size of the components of the material. A collection system may be connected to the separator system for storing the grinded material.

[0136] In other examples, a separator system may be dispensed with, and a collection system 19 may be directly arranged with the jar 2, see e.g. figure 5. In some examples, the collection system 19 may be connected to the jar 2 in a sealed manner after the rotation of the base 5, and therefore of the jar 2, has stopped. An under pressure may be applied for helping the milled material to advance to the collection system 19. In other examples, the collection system 19 may be already secured to the jar 2 before rotation of the base 5 has started, and therefore the milled material may advance to the collection system 19 due to the rotation. A lateral portion of the jar 2 may comprise through holes for allowing the material to pass to the collection system 19. For example, a bottom lateral portion of the jar 2 may comprise a plurality of through holes.

[0137] In some examples, the produced (nano)particles may be processed further after they have been produced.

[0138] Explanations and details of the ball mill system described for example with respect to figures 1 - 5 may be applied and combined with method 20, and vice versa.

[0139] This written description uses examples to disclose a teaching, including the preferred embodiments, and also to enable any person skilled in the art to put the teaching into practice, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques within the scope of this disclosure. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.

Claims

25CLAIMS1. A ball mill comprising: a housing; a base arranged within the housing and configured to rotate in a first direction around an axis perpendicular to the base; and a jar eccentrically mounted on the base; wherein the base and / or the jar comprises a resilient flexible coupling for supporting the jar on the base.

2. The ball mill of claim 1, wherein an inner lateral surface of the ball mill housing comprises at least one electromagnet and the jar comprises at least a magnetic or ferromagnetic portion.

3. The ball mill of claim 1 or claim 2, further comprising a vibrating platform for supporting the jar.

4. The ball mill of any of claims 1 - 3, wherein the jar is configured to rotate with respect to the base and around an axis extending along a longitudinal direction of the jar.

5. The ball mill of claim 4, further comprising an input pulley arranged with a base shaft for rotating the base, an output pulley arranged with a shaft for rotating the jar, and a belt connecting the input pulley and the output pulley.

6. The ball mill of any of claims 1 - 5, wherein the base comprises a slot along which the jar can move between a first position closer to a center of the base and a second position further away from the center of the base than the first position.

7. The ball mill of claim 6, further comprising a track below the slot to which the jar can be slidably connected for moving the jar along the slot.

8. The ball mill of claim 7, wherein the slot is curved.

9. A method for grinding material comprising:introducing a material to be grinded in a jar; introducing a plurality of grinding balls in the jar; reducing a size of the material by rotating the jar and by wobbling the jar.

10. The method of claim 9, wherein the grinding balls comprise an outer hollow ball including through holes and an inner ball inside the outer hollow ball.

11. The method of claim 9 or claim 10, further comprising connecting the jar to a rotatable base, and rotating the rotatable base.

12. The method of claim 11 , wherein rotating the base comprises varying a speed of rotation of the base.

13. The method of claim 11 or claim 12, further comprising mounting the jar on the rotatable base, wherein mounting the jar on the base comprises arranging the jar at a specific position along a slot in the base.

14. The method of any of claims 9 - 13, wherein the jar includes a plurality of compartments, and a size of the grinding balls decreases from a top compartment to a lower compartment.

15. The method of any of claims 9 - 14, wherein reducing the size of the material comprises obtaining nanoparticles.

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