APPARATUS AND METHOD FOR GRINDING MATERIAL INTO PARTICLES

Abstract

An apparatus and method for grinding particulate material comprises: a vertical roller mill comprising a grinding table and a grinding roller having an axis of rotation, each of which has a grinding surface and is arranged to define a grinding zone between the grinding surfaces, and a feeder for feeding particulate material to the vertical roller mill; wherein the grinding roller is arranged to roll around a grinding path on said grinding table; and the feeder is arranged to receive a supply of the particulate material and to direct a flow of that material to the grinding zone of the vertical roller mill;The feeder can be positioned to substantially restrict the flow of material to a predetermined defined cross-section, to direct the flow of material by applying a thrust and / or pushing, or to compact the flow of material before directing the material, or combinations thereof; in particular, the description is applicable to grinding particulate materials such as mined minerals, industrial minerals and chemicals, sand, slag, ash, clay, coating pigments, pharmaceuticals, and cement raw materials.

Description

APPARATUS AND METHOD FOR GRINDING MATERIAL INTO PARTICLES TECHNICAL FIELD The present description relates to a vertical roller mill apparatus and respective method of operation for grinding particulate material, in particular, but not necessarily, mining minerals, industrial minerals and chemicals, sand, slag, ash, clay, coating pigments, pharmaceuticals, cement production and cement raw materials. BACKGROUND OF THE INVENTION Vertical roller mills are used to grind various types of particulate materials, such as extracted minerals, industrial minerals and chemicals, sand, slag, ash, clay, coating pigments, pharmaceuticals, limestone, cement clinker, slag sand, old concrete, and materials from the mineral, mining, and other industries. These materials can be granular, powdered, or particulate; generally, brittle materials, including all types of granular or particulate materials used in industrial and chemical production, or in the chemical or pharmaceutical industries, particularly in the production of cement or cement raw materials. Traditional vertical roller mill devices suffer from a number of limitations. A limitation of traditional vertical milling equipment is that the material in the grinding zone can only be enclosed by two surfaces, the grinding surfaces, leaving the sides of the grinding zone open and allowing material to escape the pressure. This severely limits the effective grinding width to a small fraction of the grinding surface width, resulting in excessively wide, heavy, and expensive grinding rolls and tables with low efficiency. Furthermore, in a traditional vertical roller mill, the particulate material is added to the middle of the grinding table and is conveyed or flows across the table to the grinding surface and into the grinding zones assisted by the table's rotation. At a certain rotational speed, most of the material leaves the table without passing through the grinding zones under the rollers due to the centrifugal force created by the rotation of the grinding table. This limits the operating speed and thus the grinding capacity of the vertical roller mill. With increasing speeds and fineness, the grinding bed generally becomes less stable due to several factors, one being believed to be trapped air in the material and another being an irregular supply of material to the grinding zone. This instability limits the fineness that can be economically achieved in a traditional vertical roller mill. Adding water to the material can, to some extent, alleviate the instability of the grinding bed. However, adding water is undesirable for many materials, such as cement, as it affects product quality. Furthermore, adding water increases operating costs. In traditional vertical roller mills, instability of the grinding bed is a cause of strong and potentially damaging roller vibrations. Since mills are typically operated near their maximum operating speed to maximize capacity, vibrations are common and a problem in many plants. For example, document EP0112022A2 describes a vertical roller mill with a grinding table, rollers, and a separator to separate the grinding material. As another example, document WO2013 / 143565A1 describes a vertical roller mill that is suitable for the cement industry and the grinding of wet cement raw materials and includes a pre-drying device for pre-drying the wet material. These facts are described in order to illustrate the technical problem addressed by this description. BRIEF DESCRIPTION OF THE INVENTION This description relates to a vertical roller mill apparatus for grinding particulate material and the corresponding method. Other aspects of this description include: A vertical roller mill for grinding particulate material, comprising a grinding table having a shaft and one or more grinding rollers, each with a axis of rotation and positioned to define grinding zones between said grinding table and each of said rollers, and a feeder comprising conveying means, either a single one or a set of linked devices, for each roller, preferably a mechanical conveying means, for conveying particulate material to the vertical roller mill and having a proximal end and a distal end relative to the vertical roller mill, the vertical roller mill being positioned at the proximal end of the conveying means. Included in the objectives of the present description is to eliminate at least some of the limitations of known vertical roller mill apparatus for grinding particulate material, provide a cost-effective solution that produces higher throughput and capacity, reduce the need to add water for stabilization of the grinding bed, allow finer grinding than economically possible with known vertical roller mills, and reduce vibrations. An apparatus for grinding particulate material, particularly for cement production, is described, comprising: a vertical roller mill for grinding particulate material comprising a grinding table and a grinding roller having a rotating axis, each table and roller having a grinding surface and positioned to define a grinding zone between the grinding surfaces of the grinding roller and the grinding table; and a feeder for feeding particulate material to the vertical roller mill; wherein the grinding roll is positioned to roll over the particulate material in a grinding path on said grinding table; and the feeder is arranged to receive a supply of the particulate material and to direct a flow of that material to the grinding zone of the vertical roller mill, in particular at a speed relative to the axis of the grinding roll of at least 0.3 times the tangential speed of the grinding surface of the grinding roll or at least 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 2.0, 3.0 or 4.0 times the tangential speed of the grinding surface of the grinding roll. The apparatus for grinding material into particles can be a grinding machine or ore extraction mill; an industrial crusher; a mineral crusher or mill; a chemical material crusher; a crusher for sand, slag, ash or clay; a pigment grinding machine; a grinding machine for use in the production of coatings, pharmaceuticals or cement. The feeder can be positioned to substantially restrict the flow of material directed to the grinding zone to a predetermined, defined cross-section. The feeder can be positioned to direct the flow of material by applying a pulse to, or pushing, or applying a pulse and pushing, the material in the grinding zone. The feeder can be positioned to compact the material flow before directing the material into the grinding zone. The feeder can be positioned to direct the flow of material to the grinding zone at an angle substantially tangential to the grinding path. The feeder can be positioned to direct the flow of material into the grinding zone at substantially the same speed as the tangential speed of the grinding roll in the grinding zone. The feeder may comprise a guide tray that is adjacent to and substantially parallel to the material flow, or adjacent to and tangential to the material flow; in particular, the guide tray is a curved tray. The feeder can be positioned to direct the flow of material in the grinding zone at an angle relative to a plane defined by the grinding surface of the grinding table, where the angle is greater than zero and less than or equal to 30°, in particular greater than zero and less than or equal to 15°, and in particular greater than zero and less than or equal to 10°, and in particular greater than zero and less than or equal to 5°. The device may include: one or more additional grinding rollers; each having a rotation axis and a grinding surface, and being arranged to define a respective grinding zone between the grinding surface of the grinding roller and the grinding table; wherein one or more additional grinding rollers are positioned to roll over the particulate material in one or more additional grinding paths on said grinding table. The device may include: one or more additional feeders to feed the particulate material to the vertical roller mill; where one or more additional feeders are each positioned to receive a supply of the particulate material and to direct a flow of that material to the respective grinding zone of a grinding roller. The feeder may comprise at least one conveyor belt comprising at least two pulleys and a belt extending around said pulleys. The feeder may comprise two belt sections arranged opposite each other with respect to the particulate material to restrict the particulate material between the two belt sections. The two opposite sections of the belt can form a funnel with an opening to receive the particulate material; the funnel has an opening angle of at least 0.5, 1, 5, 10, 15, 20, 25, 30, 40, 50, 60 or 70 degrees between the sections of the belt that form the funnel. The feeder may comprise at least one diverter drum that diverts a first section of the belt into a second section between two pulleys to impart a curved shape to the first section. The deflection drum may comprise a plurality of holes on the peripheral surface; in particular, the holes are blind holes. The deflection drum may comprise a plurality of separate wheels that engage the belt. The deflection drum may comprise a plurality of projections. The feeder may comprise at least one screw conveyor comprising a rotating helical screw blade. The feeder may comprise at least one stationary gravity feeder such as a pipe, duct, or plate. The feeder may comprise a set of linked sub-feeders arranged to form a combined flow of material and to direct the flow to the grinding zone of the vertical roller mill. The grinding table and grinding rollers of the vertical roller mill can be driven by independent motors. One or more feeders, grinding rolls or grinding table may comprise independent drive mechanisms that operate independently of each other, including the feeder or feeders that operate independently of the vertical roller mill table or the vertical mill roll or rolls that operate independently of the vertical mill table; or the feeder or feeders, the mill table and the roll or rolls may be operated independently. The grinding table and grinding rollers of the vertical roller mill can be fixed relative to each other, except for rotation, at a predetermined adjustable distance, thus creating a fixed grinding zone. The apparatus can be configured to be operable at a speed by giving the grinding surface of the grinding roller a tangential speed of at least 2 m / s or at least 4, 6, 8, 10, 12, 14, 16, 19, 22, or 25 m / s. The vertical roller mill may comprise an inner grinding zone support device that extends axially away from the grinding table, beyond the grinding surface of the grinding table, being substantially concentric with the axis of rotation of the grinding table and having an outside diameter equal to 0.8 to 1.0 times the inside diameter of the grinding surface of the grinding table. The vertical roller mill may comprise at least one outer grinding zone support device extending radially beyond the grinding surface of the grinding roller, having a surface facing the grinding table, and said surface being located axially at a distance from the axis of rotation of the grinding table of 1.0 to 1.1 times the outer radius of the grinding surface of the grinding table measured in a plane coincident with the grinding surface of the grinding table and perpendicular to the axis of rotation of the grinding table, such that the surface of the outer grinding zone support device facing the grinding table provides lateral support for the material flow in the zone. IVIA / S / ZUZZ / UI 004 1 grinding and thus reduce the lateral spillage of material. A method for grinding material into particles is also described, in particular a method for operating any apparatus described, comprising the steps of: receive a supply of particulate material; form a flow of the particulate material; using a feeder to direct the flow of particulate material to a grinding zone of a vertical roller mill comprising a grinding table and a grinding roller having a rotating axis, each table and roller having a grinding surface and arranged to define said grinding zone between the grinding surfaces of the grinding roller and the grinding table, the grinding roller being arranged to roll over the particulate material in a grinding path on said grinding table, in particular at a speed relative to the axis of the grinding roller of at least 0.3 times the tangential speed of the grinding surface of the grinding roller or at least 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 2.0, 3.0 or 4.0 times the tangential speed of the grinding surface of the grinding roller; and grinding the particulate material in the vertical roller mill. The particulate material can be directed to the grinding zone of the vertical roller mill in a substantially straight direction, i.e., without substantial directional change between the feeder and the grinding zone other than that caused by gravity. The method may involve compacting the material flow by imposing a change of direction through the application of a centrifugal force. The particulate material can be directed to the grinding zone at a speed relative to the roller axis of at least 0.6 times the tangential speed of the grinding surface of the grinding roller or at least 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or 2.0 times the tangential speed of the grinding surface of the grinding roller relative to the grinding table. The method may comprise providing an airflow substantially parallel to and in contact with the flow of the material being transferred and is characterized by the airflow having a velocity between 0.5 and 3 times the velocity of the particulate material flow, such as at least 0.5 times the velocity of the material or at least 0.6, 0.8, 1.0, 1.2, 1.4 or 2.0 times the velocity of the material. Forming a particulate material flow can involve combining several material flows to provide a common material flow. The method may comprise supporting the particulate material in the grinding zone on at least one side of the grinding zone to reduce the escape of particulate material from the volume between the grinding surfaces. BRIEF DESCRIPTION OF THE DRAWINGS The following figures provide preferred ways to illustrate the description and should not be seen as limiting its scope. Figures 1A to 11 show some ways to implement what is understood as a vertical roller mill in the context of this description. Figures 2 to 14 each show one way to implement this description or a specific part of it. Figure Ox is a cross-sectional representation of a known vertical roller mill. Figure 0A shows the pressure profile in the grinding zone of known vertical roller mills. Figure 0B shows the pressure profile in the vertical roller mills of the grinding zone in an apparatus according to the description. Figure 1A is a schematic representation of one type of vertical roller. Figure lBx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure 1C is a schematic representation of an additional modality of a vertical roller mill. Figure lDx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure lEx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure lFx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure 1G is a schematic representation of an additional modality of a vertical roller mill. Figure lHx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure II is a schematic representation of an additional modality of a vertical roller mill. Figure 1J is a schematic representation of an additional modality of a vertical roller mill. Figure lKx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure lLx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure lMx is a cross-sectional representation of an additional modality of a vertical roller mill. Figure IN is a schematic representation of an additional modality of a vertical roller mill. Figure 2 is a schematic representation and a partial cross-sectional view of a first embodiment of an apparatus according to the description in which the feeder comprises a single conveyor belt, and the particulate material is transferred by means of the feeder through open air to the vertical roller mill. Figure 2A is a schematic representation and a partial cross-sectional view of a variation of the modality shown in Figure 2 and differs from it in that the feeder comprises a set of two conveyor belts joined together to form the feeder. Figure 3 is a schematic representation and a partial cross-sectional view of a second modality of an apparatus according to the description being a modification of the first modality above and wherein the material in the first section of the conveyor belt is limited by a transport guide plate, and the particulate material is transferred to the vertical roller mill supported by a nearby lower guide plate. Figure 4 is a schematic representation and a partial cross-sectional view of a third embodiment of an apparatus according to the description in which the feeder comprises a conveyor belt and an air guide through which an airflow is in contact with the material flow during the transfer of the material to the vertical roller mill. Figure 5 is a schematic representation and a partial cross-sectional view of a fourth modality of an apparatus according to the description in which the transfer of material from the feeder to the vertical roller mill is in contact with an airflow supplied by the nozzles. Figure 6 is a schematic representation and a partial cross-sectional view of a fifth modality of an apparatus according to the description in which the feeder comprises two conveyor belts placed opposite each other. Figure 7 is a schematic representation and a partial cross-sectional view of a sixth modality of an apparatus according to the description in which the feeder is a screw conveyor and the particulate material is transferred through free air to the vertical roller mill. Figure 7A is a schematic representation and a partial cross-sectional view of a variation of the sixth modality of an apparatus according to the description in which the feeder comprises two screw conveyors. Figure 8 is a schematic representation and a partial cross-sectional view of a seventh modality of an apparatus according to the description in which the feeder is a screw conveyor and the particulate material is transferred to the vertical roller mill in contact with an airflow supplied through an air guide. Figure 9 is a schematic representation and a partial cross-sectional view of an eighth modality of an apparatus according to the description in which the feeder comprises, by means of a first modality, a conveyor belt in combination with a diverter drum. Figure 9A is a schematic representation and a partial cross-sectional view of the material transfer between the feeder and the vertical roller mill supported by the proximal guide plates. Figure 9B is a schematic representation and a partial cross-sectional view of the material transfer between the feeder and the vertical roller mill in contact with an airflow supplied by the nozzles. Figure 9C is a schematic representation and partial cross-sectional view of the material transfer between the feeder and the vertical roller mill in contact with an airflow flowing in an air guide. Figure 10B is a schematic representation of an implementation of the deflection drum with blind holes of a shape other than rectangular on the peripheral surface. Figure 10C is a schematic representation of a deflection drum implementation comprising two wheels. Figure 10D is a schematic representation of a deflection drum implementation comprising bars between two wheels for coupling the material. Figure IDE is a schematic representation of a deflection drum implementation comprising projections for coupling the material. Figure 11 is a schematic representation and a partial cross-sectional view of a tenth embodiment of an apparatus according to the description in which the feeder comprises, by means of a third embodiment, a conveyor belt in combination with a deflector drum, wherein the deflector drum is positioned as two mutually separated wheels, and an airflow is in contact with the material through the feeder and during the transfer of the material to the vertical roller mill. Figure 12 is a schematic representation of one modality of a vertical roller mill where the inner and outer grinding zone support devices provide support to the sides of the material in the grinding zone. Figure 12x is a cross-sectional view of the vertical roller mill depicted in Figure 12. Figure 13 is a schematic representation of an eleventh modality of an apparatus according to the description in which the feeder comprises a stationary device with a concave surface. Figure 14 is a schematic representation of a twelfth modality of an apparatus according to the description in which the feeder comprises a stationary device with a concave surface on the lower side. Figure 15 is a schematic representation of a thirteenth modality of an apparatus according to the description in which the vertical roller mill is positioned to receive a flow of material vertically downwards from the feeder directly to the grinding zone. Figure 16 is a schematic representation of a fourteenth modality of an apparatus according to the description in which a first conveyor belt and a second conveyor belt form a funnel. DETAILED DESCRIPTION OF THE INVENTION The objective of the present description is to eliminate at least some of the limitations of known vertical roller mill apparatus for grinding particulate material, provide a cost-effective solution that produces higher throughput and capacity, reduce the need to add water for stabilization of the grinding bed, allow finer grinding than economically possible with known vertical roller mills, and reduce vibrations. Figure Ox represents a traditional vertical roller mill comprising a grinding table CO and one or more grinding rollers A0 (only one is shown) that rotate about axes DO and E0 respectively and form a grinding zone B0 between the respective grinding surfaces F0, G0. The grinding rollers move towards and away from the grinding table, and the grinding pressure in the grinding zone is regulated by applying a force to the grinding roller and allowing the roller to move according to the amount of feed to the grinding zone. The traditional vertical roller mill also includes a circumferential containment ring Q0. The height of the containment ring Q0 regulates the level of material entering the grinding zone B0, and for practical purposes, operation without the containment ring is not possible. After passing through the grinding zone, the material flows over the containment ring and is carried along. Similarly, excess feed material in front of the grinding zone flows over the containment ring and is carried along. The material feed U0 is supplied centrally to the grinding table C0 through the pipe R0 and flows through the grinding table, assisted by the rotation of the table, onto the grinding surface and into the grinding zone under the grinding roller. The SO and TO sides of the B0 grinding zone are open, allowing material to escape to the sides. As a result of this material escaping, sufficient pressure to grind the material into particles exists only within a limited portion of the grinding zone's width. A typical radial pressure profile across the grinding zone is shown in Figure 0A. This profile exhibits a high-pressure peak of limited width. Grinding occurs within this high-pressure peak area. Due to the curvature of the grinding table C0 and the potential interference with the grinding roll A0, it is not possible to bring the rotating containment ring Q0 closer to the grinding zone B0 to provide lateral support and prevent material from escaping through the outside SO of the grinding zone. Similarly, adding a rotating support surface to the inside TO of the grinding zone is not operationally feasible, as this would necessarily extend above the grinding surface of the grinding table G0 and would therefore interfere with and restrict the flow of material to the grinding zone. Attempts have been made to use stationary material guides inside the grinding surfaces and stationary containment devices near the grinding zone, including some that do not extend completely around the grinding table. However, experiments have shown that such arrangements lead to increased wear and higher energy consumption. Therefore, they have no commercial value. The description herein overcomes these limitations by providing a constant regulated material flow of suitable cross-section directed to (and towards) the grinding zone and, in particular, with a positive impulse in the direction of the grinding process by which the material is effectively forced into the grinding zone and creates a stable grinding bed. Directing the material feed to the grinding zone eliminates or substantially reduces the influence of centrifugal force on the grinding table, eliminates the need for added water for stability, eliminates the need for a containment ring, and prevents material from flowing across the grinding table. This allows for the implementation of rotating devices that support the material's sides within the grinding zone. Furthermore, the constant, regulated material flow allows both the grinding table and the grinding rolls, except for rotation, to remain fixed to each other while maintaining grinding pressure. The fixed geometry of the grinding zone greatly reduces vibrations compared to the more common arrangement with a fixed grinding table and moving rolls. Enclosing or supporting the sides of the grinding zone leads to a radial pressure profile across the grinding zone, as shown in Figure 0B. The width of the high pressure zone is greatly increased compared to the traditional arrangement, and grinding can occur over a much larger portion of the grinding surface, thus increasing the grinding capacity. A modality of the vertical roller mill in an apparatus according to the description, where the sides of the grinding zone are enclosed or supported, is shown in Figure 12 and Figure 12x. The term vertical roller mill refers to a grinding device comprising a grinding table having a shaft and at least one grinding roller having an axis of rotation. This axis of the grinding table is perpendicular to a plane defined by the grinding table and passes through the geometric center of the grinding path. It is positioned to define the grinding zones between the grinding surface of the grinding table and the grinding surface of each of the rollers. The grinding roller(s) are positioned to roll around the grinding path on the grinding table. The grinding table may or may not rotate about its axis. The grinding table may be positioned below, alongside, or above the roller(s) with the axis vertical, or with the axis at any angle between vertical and horizontal in any direction.The grinding zone(s) is / are formed between the grinding surfaces of the roller(s) and the grinding surface of the grinding table and may be substantially rectangular or any other shape in cross-section, with linear or curved edges, or any combination thereof. Figures 1A to IN represent some variations of what is understood as a vertical roller mill but should not be interpreted as excluding other vertical roller mill arrangements. The term grinding zone refers to the volume between a grinding roll and the grinding surfaces of the grinding table where particulate material is gripped, compressed, and / or crushed by the grinding roll and the grinding table. In the context of this description, it should be understood that the supply or direction of material to the grinding zone includes arrangements where material is transferred directly to one of the grinding surfaces before gripping can occur and then follows that surface into and through the grinding zone. The term feeder should be understood as a device that accelerates and / or transports particulate material. Feeders include conveyor belts, chain conveyors, belt launchers, screw conveyors, vibratory conveyors, pipes, ducts, and more. The term restricted material flow refers to material flow with a predetermined, defined cross-section, without necessarily being physically limited by physical means. The flow may be restricted by the way it projects from the feeder, by physical means, or by a combination of both. When limited to a defined cross-section, directed material flow may take the form of a mat, particularly one with a rectangular cross-section. The term "compact a material flow" means that the material supplied to the feeder, during contact with the feeder, undergoes a change in cross-sectional shape, cross-sectional size, and / or experiences a change in apparent density due to a change in the volume of voids within the material flow, and / or the material combines with another material flow to form a common combined flow. The term "united device assembly" refers to any number of conveying means, similar or of different types, operating simultaneously to transfer material to a single grinding unit. Individual conveying means may be supplied with material from the same source or from separate sources and may be operated independently, at different speeds and / or feed rates. Furthermore, the conveying means may share common components, such as a common housing, casing, or guide plate. The apparatus, as described, is characterized in that the feeder is positioned and configured to receive a supply of particulate material and to form, and preferably restrict, a flow of the material and to direct the flow of particulate material to a grinding zone of the vertical roller mill. The flow is supplied directly by the feeder to the grinding zone under acceleration, compaction, and / or cross-sectional restriction. One aspect of the description refers to the feeder that is positioned to limit the flow of material to a defined cross-section; this cross-section is defined by the flow of material between the feeder and the grinding zone. One aspect of the description refers to the feeder that is positioned to direct the flow of material by pushing a compact flow of material into the grinding zone. One aspect of the description refers to the feeder that is positioned to direct the flow of material by applying a boost to the material in the grinding zone. In one iteration of the description, the material flow is directed to the grinding zone at an angle that is substantially tangential to the grinding path. In this way, the efficiency and stability, and thus the speed, of the grinding process can be improved. An inlet device configured to supply the particulate material to the feeder may be included in the apparatus. The inlet device may preferably be positioned at the distal end of the feeder. In one embodiment of the apparatus according to the description, the feeder comprises a conveyor belt. The belt is an endless belt that rotates around two spaced conveyor pulleys, one of which is a drive pulley. The drive pulley is preferably located at the distal end of the feeder. The feeder may comprise a single conveyor belt having a first section where particulate material is supplied from, for example, a feed container to form a material flow in the first section. In one variation of this design, the feeder comprises two or more conveyor belts as described above, joined together to form a material flow and transfer it to the grinding zone. The individual conveyors in the assembly can be operated at different speeds to provide optimal flow in the grinding zone. In a further embodiment of the apparatus described, the feeder comprises two opposing, parallel conveyor belts. The opposing conveyor belts physically confine and accelerate the supplied particulate material into the space between them at the desired velocity. In a further embodiment of the apparatus as described, the feeder comprises two conveyor belts positioned so that there is an angle between two opposite sections of the belt forming a funnel to grasp and accelerate the material. The angle between the sections of the belt is greater than zero and less than or equal to 90°, preferably less than or equal to 70°, in particular greater than zero and less than 5 degrees, or less than 10, 15, 20, 25, 30, 40, 50, 60, or 70 degrees. A funnel-like belt configuration provides enhanced compression of the particulate material, increasing the density and compaction of the fed material by wedging the material between the belts so that the material does not slip against the belt surfaces as it is fed to the grinding surface. The angle will typically depend on the friction between the belts and the material. A lower coefficient of friction will generally require a shallower funnel opening angle so that the material does not slip relative to the belts. Conversely, a higher coefficient of friction will generally allow for a steeper funnel opening angle so that the material can be compacted over a shorter distance. According to an additional embodiment of an apparatus as described, the feeder comprising a conveyor belt may further comprise a transport guide plate positioned opposite and parallel to a section of the conveyor belt that is oriented towards the guide plate and carries the particulate material. According to a further embodiment of the apparatus described, the feeder comprises a screw conveyor. The screw conveyor comprises a screw with a helical screw blade in a housing with an inlet end and an outlet end. The material supplied to the screw conveyor at the inlet end is accelerated and / or conveyed by the rotation of the screw and projected from the outlet end of the screw conveyor into the grinding zone of the vertical roller mill. The outlet of the screw conveyor housing can be shaped to limit the material flow to a particular cross-sectional shape, for example, rectangular, thereby forming a mat of material to be fed into the grinding zone. According to a variation of the previous embodiment of an apparatus as described, the feeder comprises an assembly of several connected screw conveyors. The assembly may comprise screw conveyors with individual housings or may comprise an assembly of screws with helical screw blades in a common housing. In a further embodiment of an apparatus according to the description, the feeder comprises a stationary device, for example, a pipe, duct, or plate, with a stationary concave surface. The material is fed at high velocity to the stationary device and flows over the concave surface. As the material flows along the concave surface, it is compacted and confined due to the centrifugal force applied by the change in direction. The flow exits the curve and is directed to a grinding zone of the vertical roller mill. According to a further embodiment of the apparatus as described, the feeder comprises a conveyor belt in combination with a deflector drum that diverts a first section of the belt into a second section between two conveyor pulleys, thereby imparting a curved shape to the first section. Particulate material is supplied to the distal end of the belt or to the deflector drum and enclosed in the space between the deflector drum and the first section of the belt. During movement through the curvature of the belt, the particulate material is accelerated to the belt speed and forms a material flow directed to the grinding zone of the vertical roller mill. In a variation of this mode, the diverter drum may comprise two or more mutually separated wheels that couple the first section of the belt. In a further variation of this embodiment, the deflection drum may comprise a plurality of holes in its peripheral surface. The holes may be blind holes. The holes may be rectangular in cross-section or have any other shape. In a further variation of this embodiment, the deflector drum may comprise a plurality of projections that engage with the particulate material and / or at least substantially engage with the surface of the belt. The projections may be at least the width of the material flow, or they may be less than the width of the material flow and / or arranged in a staggered pattern. Furthermore, the projections may be perpendicular to the plane of rotation of the deflector drum or may be at any angle with respect to this plane. According to a further embodiment of the apparatus described, the feeder comprises a chain conveyor comprising at least one endless chain with crossbars for engaging and conveying the particulate material, which runs around two chain wheels spaced apart. The feeder may further comprise a guide tray adjacent to and parallel with the section of chain that conveys the material. According to the embodiment of an apparatus as described herein, the vertical roller mill may be further provided with an inner grinding zone support device. This inner grinding zone support device extends along the axis of the grinding table, away from the grinding table and beyond its grinding surface. The device is substantially concentric with the axis of the grinding table and has an outer diameter equal to 0.8 to 1.0 times the inner diameter of the grinding surface, such that the circumferential surface of the inner grinding zone support device supports the flow of material in the grinding zone to reduce lateral spillage. Preferably, the outer diameter of the device is 1.0 times the inner diameter of the grinding surface radius less than 1 to 20 mm.The support device for the inner grinding zone may be part of the grinding table or a separate component. Preferably, the device is stationary relative to the grinding table. The outer circumferential surface that supports the material in the grinding zone may be cylindrical, conical, curved, or any combination thereof. In addition to the modalities of an apparatus according to the present description, the vertical roller mill may be provided with at least one outer grinding zone support device extending radially beyond the grinding surface(s) of the grinding roller, having one or more surfaces facing the grinding table, and such surface being located axially at a distance from the axis of the grinding table of 1.0 to 1.1 times the outer radius of the grinding surface of the grinding table measured in a plane coincident with the grinding surface of the grinding table and perpendicular to the axis of the grinding table, so that the surface(s) of the outer grinding zone support device facing the grinding table provide lateral support for the flow of material in the grinding zone and thereby reduce lateral spillage of material.Preferably, said surface is located at a distance from the axis of the grinding table in said plane of 1.0 times the outer radius of the grinding surface of the grinding table plus 1 to 20mm. The support device(s) for the outer grinding zone may be part of the roller(s) or a separate device(s). Preferably, the device rotates with the grinding roller. The surface(s) supporting the material in the grinding zone(s) may be flat, conical, or otherwise curved, or any combination thereof. According to a further embodiment of the apparatus described herein, the axis of rotation of the grinding table is positioned between the vertical and 90° with respect to the vertical, in a plane substantially parallel to the axis of the grinding table and the direction of material flow, such as between substantially the vertical and 30° with respect to the vertical, or such as between substantially the vertical and 15° with respect to the vertical. According to an alternative embodiment of the apparatus, the axis of rotation of the grinding table is positioned between substantially the horizontal and 45° with respect to the horizontal, such as between substantially the vertical and 30° with respect to the horizontal, or such as between substantially the horizontal and 15° with respect to the horizontal. According to a further embodiment of the apparatus as described, for example, for each conveying means of the feeder, it may further comprise a guide device that directs the material flow to the grinding zone and comprises a single proximal guide plate, preferably flat, or two oppositely arranged proximal guide plates, preferably flat, said guide plate or plates being arranged between the proximal end of the conveying means and the grinding zone of the vertical roller mill. Two oppositely arranged proximal guide plates may be substantially parallel or converge in the direction from the conveying means to the vertical roller mill. In a further embodiment of an apparatus according to the description, the material flow over / in the feeder and / or between the feeder and the grinding zone of the vertical roller mill is positioned so as to be in contact with an airflow substantially parallel to the material flow, with a velocity on the scale of 0.5 to 3 times the material flow velocity, such as at least 0.5 times the flow velocity or at least 0.6, 0.8, 0.9, 1.0, 1.1, 1.3, 1.4, or 2.0 times the flow velocity. The airflow velocity prevents material friction with the air from deflecting the outer material in the flow away from the direction toward the grinding zone and thus reduces the dispersion of the material being transferred to the grinding zone. The airflow parallel to the material flow is achieved by guiding the air with at least one plate substantially parallel to the flow of the particulate material.In an alternative variation of this mode, the airflow is achieved by an arrangement of at least one nozzle through which the air is projected along the surface of the particulate material flow. In a further embodiment of an apparatus according to the description, the grinding table of the vertical roller mill is fixed in place, except for its rotational movement, and the IVIA / S / ZUZZ / UI 004 1 The roller(s) move toward and away from the grinding table so that the grinding zone(s) is / are adjustable. However, it should be noted that the rollers can be fixed and the grinding table movable, and furthermore, both the grinding table and the rollers of the vertical roller mill can be fixed relative to each other during operation in a preferred arrangement to provide a constant grinding zone(s). The vertical roller mill can be driven by motors on the grinding table, on the rollers, or both. In one embodiment of an apparatus according to the description, the grinding roller(s) and the grinding table are driven individually and the speed of each can be adjusted independently to achieve optimal conditions in the grinding zone(s). In one embodiment of an apparatus according to the description, the feeder is operable at a speed that provides the flow of particulate material at a speed of at least 2 m / s or at least 4, 6, 8, 10, 12, 14, 16, 19, 22, or 25 m / s in the grinding zone. In one modality of the apparatus according to the description, the particulate material is selected from mining minerals, industrial minerals and chemicals, sand, slag, ash, clay, coating pigments, pharmaceuticals and cement raw materials. The vertical roller mill of the apparatus according to the description is preferably operable independently of the feeder, so it is possible to adapt the operation of the feeder to the operation of the vertical roller mill and vice versa in order to obtain smooth and reliable operation of the apparatus and thus the desired performance and capacity of the apparatus. The apparatus according to the description refers to a method for grinding particulate material comprising receiving a supply of particulate material, forming a flow, directing the particulate material to a grinding zone of a vertical roller mill, and grinding the particulate material in the vertical roller mill. The method may further comprise that the particulate material is directed from the feeder to the grinding zone of the vertical roller mill without substantial directional change and / or that the particulate material is directed to the grinding zone at a speed of at least 0.6 times the peripheral speed of the grinding roller or at least 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or 2.0 times the tangential speed of the grinding surface of the grinding roller. According to the description, by feeding the material flow at substantially the same or similar speed as the relative rotation between the grinding roller and the grinding table, the efficiency and stability, and thus the speed, of grinding is improved. The method may further comprise providing an airflow substantially parallel to and in contact with the flow of the material being transferred and is characterized by the airflow having a velocity between 0.5 and 3.0 times the velocity of the particulate material flow, such as at least 0.5 times the velocity of the material or at least 0.6, 0.8, 1.0, 1.2, 1.4 or 2.0 times the velocity of the material. This section explains the types of vertical roller mills shown. It should not be interpreted as excluding other types of vertical roller mills. Figure 1A shows a vertical roller mill comprising a grinding roller A, with a grinding surface F rotating about an axis E, and a grinding table C, with a grinding surface G rotating about an axis D, arranged to create a grinding zone B between the grinding surfaces F, G. In this embodiment, the axes E, D of the grinding roller A and the grinding table B are substantially perpendicular and the grinding roller has a substantially cylindrical shape. Figure 1Bx shows a cross-section of a vertical roller mill comprising a grinding roller Al, with a grinding surface F1 rotating about an axis El, and a grinding table Cl with a grinding surface G1 rotating about an axis DI, positioned to create a grinding zone B1 between the grinding surfaces F1 and G1. In this embodiment, the grinding surface F1 of the grinding roller Al is substantially conical, while the grinding surface G1 of the grinding table Cl is substantially flat. The angle H1 between the axes of rotation El and DI is greater than 90 degrees. The grinding surfaces F1 and G1 in the cross-section of the grinding zone B1 are substantially parallel. Figure 1C shows a vertical roller mill comprising a grinding roller A2, and a grinding table C2. In this embodiment, the grinding surface F2 of the grinding roller A2 is conical and the grinding surface G2 of the grinding table C2 is inwardly conical. Figure 1Dx shows a cross-section of a vertical roller mill comprising a grinding roller A3 and a grinding table C3. In this embodiment, the grinding surfaces F3, G3 of the grinding roller A3 and the grinding table C3 are curved in cross-section in the grinding zone B3. Figure 1Ex shows a cross-section of a vertical roller mill comprising a grinding roller A4 and a grinding table C4. In this embodiment, the grinding surface F4 of the grinding roller A4 is conical and the grinding surface G4 of the grinding table C4 is outwardly conical. The cross-section of the grinding zone B4 shows the substantially straight contours of the grinding surfaces F4 and G4. Figure 1Fx shows a cross-section of a vertical roller mill comprising a grinding roller A5 and a grinding table C5. In this embodiment, the grinding surface F5 of the grinding roller A5 is cylindrical, and the grinding surface G5 of the grinding table C5 is outwardly conical. The contours of the grinding surfaces F5 and G5 are substantially straight in cross-section in the grinding zone B5. In this embodiment, the angle H5 between the axes of rotation D5 and E5 of the grinding table C5 and the grinding roller A5, respectively, is less than 90 degrees. Figure 1G shows a vertical roller mill comprising two grinding rollers A6, J6, rotating about axes E6, L6, with grinding surfaces F6, M6, and a grinding table C6 rotating about an axis D6, with a grinding surface G6, arranged to create grinding zones B6, K6 between grinding surfaces G6, and M6, G6. Figure lHx shows a cross-section of a vertical roller mill comprising a grinding roller A7 rotating about an axis E7, with a grinding surface F7, and a grinding table C7 rotating about a horizontal axis D7, which is positioned to create a grinding zone B7 between the grinding surfaces F7, G7. Figure II shows a vertical roller mill comprising a grinding roller A8 rotating about an axis E8 and a grinding table C8 rotating about a vertical axis D8 positioned to create a grinding zone B8 between the grinding surfaces F8, G8. In this embodiment, the grinding table C8 is positioned above the grinding roller A8 so that the grinding surface G8 is on the underside of the grinding table C8. Figure 1J shows a vertical roller mill comprising a grinding roller A9 rotating about an axis E9 and a grinding table C9 rotating about an axis D9 positioned to create a grinding zone B9 between the grinding surfaces F9, G9. In this embodiment, the axis of rotation D9 of the grinding table C9 is inclined from a vertical axis N9 in a plane that is not parallel to the axis of the grinding roller E9. Figure lKx shows a cross-section of a vertical roller mill comprising a grinding roller A10 and a grinding table CIO positioned to create a grinding zone B10 between the grinding surfaces FIO, G10. This embodiment differs from that shown in Figure lEx in that the grinding surface G10 on the grinding table CIO is inwardly tapered. Figure 1Lx shows a cross-section of a vertical roller mill comprising a grinding roller A1 and a grinding table C11. This embodiment differs from that shown in Figure 1A in that the distance between the grinding surface A11 and the grinding surface B12 of the roller varies across the width of the grinding zone B12, from the inner to the outer diameter of the grinding surface A11. As shown, the distance A11 near the inner diameter of the grinding surface A11 is greater than the distance A11 near the outer diameter of the grinding surface A11 on the grinding table C11. The variation in distances between the grinding surfaces may differ in other arrangements of the vertical roller mill. Figure IMx is a cross-sectional representation of a vertical roller mill comprising a grinding roller A12 and a grinding table C12 positioned to create a grinding zone B12 between the grinding surfaces F12, G12. In this embodiment, the grinding surface of the grinding roller F12 is shaped to have multiple curves as seen in the cross-section. Figure IN shows a vertical roller mill comprising a grinding roller A13, with a grinding surface F13 rotating about axes D13 and E13, and a stationary grinding table C13, with a grinding surface G13 positioned to create a grinding zone B13 between the grinding surfaces F13, G13. As shown in Figure 2, the first embodiment of an apparatus 1 according to the present description for grinding particulate materials comprises an inlet device 2, a feeder 3, and a vertical roller mill 4. The vertical roller mill 4 for grinding particulate material supplied thereto comprises a grinding table 5 and a grinding roller 6, each with a non-parallel axis of rotation 7, 8, positioned to define a grinding zone 9. The feeder 3 is positioned and configured to convey particulate material 10 to the vertical roller mill 4 and has a proximal end 11 near the vertical roller mill 4 and an opposite distal end 12. The feeder comprises a conveyor belt 13 comprising two separate conveyor pulleys 14, 15 and an endless conveyor belt 16 extending around two conveyor pulleys 14, 15. The belt has a first span 17 and a second span 18.The belt is supplied with particulate material 10 at its distal end 12 by the inlet device 2. The inlet device comprises a feed container 19 with a lower outlet opening 20 that feeds the particulate material to the distal end of the conveyor belt 13, which is positioned below the outlet opening 20. The size of the outlet opening 20, and thus the amount of material delivered to the first section 17 of the conveyor belt 13, is adjustable by means of an adjustment device such as, for example, a gate 21. The speed of the belt 16 and the supply of particulate material from the feed container 19 through its lower outlet opening 20 and into the first section 17 of the belt are synchronized such that a flow 22 of the particulate material is formed in the first section 17 of the belt.Through the conveyor belt 13, the flow 22 is directed to the grinding zone 9 of the vertical roller mill 4. From the proximal end 11 of the conveyor belt 13, the flow 22 is projected through the air into the grinding zone 9. Figure 2A shows a variation of apparatus 1A as described, wherein the feeder comprises an array of two connected conveying media 3A, 3B. In this implementation, the particulate material 10A is delivered to the conveyors 13A, 13B from a single inlet device 2A. However, the material can also be delivered by individual inlet devices for each conveying media. The connected conveying media 3A, 3B form a combined material flow 22A that is delivered to the grinding zone 9 of the vertical roller mill 4. The second embodiment of an apparatus 301, as described in Figure 3, is a modification of the one shown in Figure 2. It differs from the latter in that the feeder 303 is provided with a conveyor guide plate 324 positioned opposite the first section 17 of the conveyor belt 13. The conveyor guide plate limits the flow 322 of the particulate material along with the first section 17 of the conveyor belt 13. Furthermore, the apparatus is provided with a lower proximal guide plate 325 positioned between the proximal end of the conveyor belt and the vertical roller mill 4. This plate supports the flow 322 during transfer to the grinding zone 9 of the vertical roller mill 4. The proximal guide plate may be omitted provided the particulate material is projected from the proximal end 11 of the conveyor belt with sufficient velocity to be transferred to the grinding zone 9. The third embodiment of an apparatus 401 according to the description shown in Figure 4 is a modification of that shown in Figure 2 and differs in that the feeder 403 of the same is provided with an air sweep guide 426 having a proximal end 428 and a distal end 429 and is arranged to direct an airflow 427 so that it is substantially parallel to and in contact with the flow 422 of the particulate material being transferred from the feeder 403 to the grinding zone 9 of the vertical roller mill 4. The air flows through the guide 426 from the distal end 429 and exits at the proximal end 428 of the guide 426. The fourth embodiment of an apparatus 501, as described in Figure 5, is a modification of the one shown in Figure 4. It differs from the latter in that its feeder 503 is provided with an airflow 527 from a nozzle 531. This airflow 527 is substantially parallel to and in contact with the particle flow 522. Furthermore, an additional nozzle 532 provides an airflow 530 below and in contact with the particulate material flow 522 between the feeder 503 and the grinding zone 9 of the vertical roller mill 4. The airflows 527 and 530 are both optional and can be provided individually without the other. The fifth embodiment of an apparatus 601 according to the description shown in Figure 6 is an alternative modification of the embodiment shown in Figure 3. Instead of the conveyor guide plate, it comprises a second conveyor belt 633 positioned separately from and parallel to the first conveyor belt 13. The first section 634 of the second conveyor belt 633 and the first section 17 of the first conveyor belt restrict the flow 622 of material. Furthermore, Figure 6 indicates that the apparatus shown may be provided with an upper proximal guide plate 635 and / or a lower proximal guide plate 636 positioned between the proximal ends 637, 11 of the conveyors 633, 13 and guiding the flow during transfer to the grinding zone 9 of the vertical roller mill 4. The sixth embodiment of an apparatus 701 according to the description shown in Figure 7 differs from the preceding embodiments in that the feeder 703 comprises a screw conveyor 738. The screw conveyor 738 comprises a housing 739, with an inlet 741 and an outlet 742, and a helical screw blade 740 for conveying the particulate material 10. As the screw blade 740 rotates, the material 10 is moved from the inlet device 702 by means of the inlet 741 through the screw conveyor 738 and projected from the outlet 742 as a through-air flow 722 of material to the grinding zone 9 of the vertical roller mill 4. The outlet 742 of the screw conveyor housing 739 can be shaped to limit the flow 722 of material to a particular cross-sectional shape, e.g., rectangular.The amount of material supplied to the vertical roller mill 4 is regulated in the inlet device 702 by means of a gate 721. The embodiment of apparatus 701A according to the description shown in Figure 7A is a variation of the embodiment shown in Figure 7 and differs from it in that the feeder 703A comprises an assembly of two screw conveyors 738A, 757A. The screw conveyors 738A, 757A, as shown, are housed in a common cover 739A. The screw conveyors, however, could have separate housings, and any number of screw conveyors can be joined together in an assembly. The seventh embodiment of an apparatus 801 according to the description shown in Figure 8 is a variation of one shown in Figure 7 and differs from it in that the flow 822 of the particulate material is in contact with an air stream 827 supplied through an air guide 826 placed at the outlet 742 of the screw conveyor 738. The air stream 827 exits the guide 843 at outlet 843 and flows parallel to and in contact with the flow 822 of the material being transferred to the grinding zone 9 of the vertical roller mill. The eighth embodiment of an apparatus 901 according to the description shown in Figure 9 comprises a feeder 903 comprising a conveyor belt 913, having two mutually spaced conveyor pulleys 914, 915 and an endless belt 916 extending between and around the pulleys 914, 915, and a deflector drum 944 that deflects the first span 917 of the belt toward the second span 918 of the belt to impart a curved shape to the first span 917. The deflector drum 944 is provided with several blind holes 945 in its peripheral outer surface 946. An inlet device 902 comprises a funnel-shaped feed chamber 947 having a lower outer opening 920 through which particulate material 910 is supplied to the distal end of the conveyor belt 913 and the deflector drum 944.The particulate material 910 is trapped in the blind holes 945 and between the outer surface of the deflector drum 946 and the first section 917 of the belt 916 and, by means of a rotational speed of the belt and the deflector drum, is projected as a flow 922 or mat of material through the air to the grinding zone 9 of the vertical roller mill 4. Furthermore, and as indicated in Figure 9A, the embodiment of the description shown may comprise an upper proximal guide plate 924 and a lower proximal guide plate 925 disposed between the proximal end of the feeder 903 and the vertical roller mill 4. The guide plates 924, 925 may converge from the proximal end of the feeder towards the vertical roller mill 4. Furthermore, the described modality may comprise an arrangement such that the air flows parallel to and in contact with the flow 922 of the material moving towards the vertical roller mill 4. The air flow 927, 930 may be supplied from nozzles 931, 932 as shown in Figure 9B or by means of a guide 926 as shown in Figure 9C. Further embodiments of the deflector drum according to the description are shown in Figures 10B to 10E. Figure 10B represents a deflector drum 1044B with a peripheral surface 1046B wherein the holes 1045B are not rectangular. Figure 10C shows a deflector drum 1044C implemented as two separate wheels 1048C having peripheral surfaces 1046C for engaging the belt. Figure 10D shows an embodiment of the deflector drum 1044D wherein bars 1049D are provided on the peripheral surface 1046D between the two wheels 1048D for engaging with the material. In a further embodiment according to the description of the deflector drum 1044E shown in Figure 10E, the deflector drum 1044E is provided with a plurality of stepped projections 1049E. The projections are positioned to be substantially radial, but they don't have to be. The embodiment of apparatus 1101, as described in Figure 11, comprises a feeder 1103 comprising a conveyor belt having two mutually spaced conveyor pulleys, a belt extending between and around the pulleys, and a deflector drum 1144 provided with two mutually spaced wheels that deflect the first section of the belt between the conveyor pulleys to the second section of the belt, imparting a curved shape to the first section. The material flow 1122 through the belt feeder is in contact with an airflow 1130 entering between the inlet device 1102 and the deflector drum. This airflow follows the flow 1122 around the curve imparted by the deflector drum and continues to the vertical roller mill 1104. The airflow may optionally be guided by an additional air guide 1126. In all other embodiments of the apparatus described herein, the vertical roller mill, as described, can be positioned as shown in Figure 12 and Figure 12x. The vertical roller mill 1204 is provided with an inner grinding zone support device 1250 extending along the axis of rotation of the grinding table 1207 away from the grinding table 1205, and beyond the grinding surface of the grinding table 1251, being substantially concentric with the axis of rotation of the grinding table 1207 such that the circumferential surface 1253 of the inner grinding zone support device 1250 provides lateral support for the material flow 1222 in the grinding zone 1209. In addition, an outer grinding zone support device 1254 is provided that extends radially beyond the grinding surface of the grinding roll 1252, is substantially concentric with the axis of rotation of the grinding roll 1208, and is located along the axis of rotation of the grinding roll 1208 at a distance from the axis of rotation of the grinding table 1207 such as not to interfere with the circumference 1255 of the grinding table 1205. The outer grinding zone support device 1254 is positioned so that the surface 1256 of the outer grinding zone support device 1254 that faces the grinding table 1205 provides lateral support for the material flow 1222 in the grinding zone 1209 and thereby reduces lateral spillage of material. The embodiment of apparatus 1301 according to the description shown in Figure 13 differs from the previous embodiments in that the feeder 1303 is a plate 1358 with a concave surface 1359. The particulate material 1310 is supplied and continues along the concave surface 1359, thereby forming a flow 1322 that exits the surface 1359 in such a direction that it is transferred to the grinding zone 9 of the roller mill 4. The plate could alternatively be a pipe, conduit, or any other device with a concave surface. This modality may optionally comprise any of the additions shown in Figures 9A, 9B and 9C, an upper proximal guide plate 924, a lower proximal guide plate 925, air flows 927, 930 through nozzles 931, 932 or an air guide 926 disposed between the proximal end of the feeder 1303 and the vertical roller mill 4. The embodiment of apparatus 1401 according to the description shown in Figure 14 is similar to the previous embodiment in that the feeder 1403 is a plate 1458 with a concave surface 1459. The particulate material 1410 flows on the underside and continues along the concave surface 1459, thereby forming a flow 1422 that exits the surface 1459 in such a direction that it is transferred to the grinding zone 9 of the roller mill 4. The plate could alternatively be a pipe, conduit, or any other device with a concave surface. In the embodiment of apparatus 1501 as described in Figure 15, the vertical roller mill 1504 is positioned to receive a material flow 1522 vertically downward from feeder 1502 directly into the grinding zone 1509. Feeder 1502 comprises two conveyor belts 1513, each comprising three pulleys 514 and one belt 1516. One section of belt 1562 is positioned at an angle 1564 to the opposite section of belt 1562 so that the belts form a funnel 1560 for the granular material 1510. As the material 1510 flows through the funnel, it is wedged between the two belt sections at an angle 1562 and accelerated to the speed of the belts 1516. In the next section of the belts 1561, the belts are positioned parallel to each other to confine and form a mat. of material 1522 between the belts 1561. The mat of material 1522 then goes to the grinding zone 1509 of the vertical roller mill 1504. The embodiment of apparatus 1601 according to the description shown in Figure 16 is an alternative modification of the embodiment shown in Figure 6. At the distal end, a first section 1634 of a second conveyor belt 1633 is arranged at an angle 1664 with the first section 17 of the first conveyor belt 13 so that they form a funnel 1660. The granular material 1610 is conveyed along the first section 17 of the first belt 13 until it is wedged between the two sections of belt 17, 1634 and accelerated to the speed of belts 13, 1633 before being directed to the grinding zone 9 of the vertical roller mill 4. The term "comprising" whenever used in this document is intended to indicate the presence of established features, integers, steps, components, but not to preclude the presence or addition of one or more features, integers, steps, components, or groups thereof. Those skilled in the art will appreciate that, unless otherwise stated in this document, the particular sequence of steps described is for illustrative purposes only and may vary without departing from the description. Therefore, unless otherwise stated, the steps described are in no particular order, meaning that, where possible, the steps may be performed in any convenient or desirable order. Furthermore, it should be understood that the description encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, descriptive terms, etc., of one or more of the claims or relevant portions of the description are introduced into another claim. For example, any claim that is dependent on another claim may be modified to include one or more limitations found in any other claim that is dependent on the same base claim. The description should in no way be restricted to the modalities described, and a person with ordinary experience in the technique will foresee many possibilities for modifications of it. The modalities described above are combinable. The following claims further set forth particular modalities of the description.

Claims

1. An apparatus for grinding particulate material, characterized in that it comprises: a vertical roller mill for grinding the particulate material and comprising a grinding table and a grinding roller having an axis of rotation, each table and roller having a grinding surface and positioned to define a grinding zone between the grinding surfaces of the grinding roller and the grinding table; and a feeder for feeding the particulate material to the vertical roller mill; wherein the grinding roller is positioned to roll over the particulate material in a grinding path on said grinding table; and the feeder is arranged to receive the particulate material and to direct a flow of that material to the grinding zone of the vertical roller mill, at a speed relative to the axis of the grinding roller of at least 0.3 times the tangential speed of the grinding surface of the grinding roller or at least 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 2.0, 3.0 or 4.0 times the tangential speed of the grinding surface of the grinding roller.

2. The apparatus according to the preceding claim, further characterized in that the feeder is positioned to direct the flow of material in the grinding zone at substantially the same speed relative to the axis of the grinding roll as the tangential speed of the grinding roll in the grinding zone.

3. The apparatus according to any of the preceding claims, further characterized in that the feeder is positioned to substantially restrict the flow of material directed to the grinding zone to a predetermined defined cross-section 4. The apparatus according to any of the preceding claims, further characterized in that the feeder is positioned to direct the flow of material by applying a pulse to, or pushing, or applying a pulse and pushing, the material in the grinding zone.

5. The apparatus according to any of the preceding claims, further characterized in that the feeder is positioned to compact the flow of material before directing the material into the grinding zone.

6. The apparatus according to any of the preceding claims, further characterized in that the feeder is positioned to direct the flow of material to the grinding zone at an angle substantially tangential to the grinding path.

7. The apparatus according to any of the preceding claims, further characterized in that the feeder comprises a guide tray that is adjacent to and substantially parallel to the material flow, or adjacent to and tangential to the material flow, in particular the guide tray is a curved tray.

8. The apparatus according to any of the preceding claims, further characterized in that the feeder is positioned to direct the flow of material in the grinding zone at an angle with respect to a plane defined by the grinding surface of the grinding table, wherein the angle is greater than zero and less than or equal to 30°, in particular greater than zero and less than or equal to 15°, and in particular greater than zero and less than or equal to 10°, and in particular greater than zero and less than or equal to 5°.

9. The apparatus according to any of the preceding claims, further characterized in that the feeder comprises at least one conveyor belt comprising at least two pulleys and a belt extending around said pulleys.

10. The apparatus according to the preceding claim, further characterized in that the feeder comprises two belt sections arranged opposite each other with respect to the particulate material to restrict the particulate material between the two belt sections.

11. The apparatus according to the preceding claim, further characterized in that the two opposite sections of the belt form a funnel with an opening to receive the particulate material, the funnel having an opening angle of at least 0.5, 1, 5, 10, 15, 20, 25, 30, 40, 50, 60 or 70 degrees between the sections of the belt forming the funnel.

12. The apparatus according to claim 9, 10 or 11, further characterized in that the feeder comprises at least one deflection drum that deflects a first section of the belt towards a second section between two pulleys to impart a curved shape to the first section.

13. The apparatus according to claim 12, further characterized in that the deflection drum comprises a plurality of holes in the peripheral surface, in particular, the holes are blind holes.

14. The apparatus according to claim 12, further characterized in that the deflection drum comprises a plurality of separate wheels that engage the belt.

15. The apparatus according to claim 12, further characterized in that the deflection drum comprises a plurality of projections.

16. The apparatus according to any of the preceding claims, further characterized in that the feeder comprises at least one screw conveyor comprising a rotating helical screw blade.

17. The apparatus according to any of the preceding claims, further characterized in that the feeder comprises at least one stationary feeder such as a pipe, a conduit or a plate.

18. The apparatus according to any of the preceding claims, further characterized in that the feeder comprises a set of joined sub-feeders arranged to form a combined flow of material and to direct the flow to the grinding zone of the vertical roller mill.

19. The apparatus according to any of the preceding claims, further characterized in that the grinding table and the grinding rollers of the vertical roller mill are driven by means of independent motors.

20. The apparatus according to any of the preceding claims, further characterized in that one or more of the feeders, grinding rolls or grinding table comprise independent drive mechanisms that operate independently of each other, including the feeder or feeders that operate independently of the vertical roller mill table or the vertical mill roll or rolls that operate independently of the vertical mill table; or the feeder or feeders, the mill table and the roll or rolls are operated independently.

21. The apparatus according to any of the preceding claims, further characterized in that it comprises: one or more additional grinding rollers; each having an axis of rotation and a grinding surface, and being arranged to define a respective grinding zone between the grinding surface of the grinding roller and the grinding table; wherein one or more additional grinding rollers are positioned to roll over the particulate material in one or more additional grinding paths on said grinding table.

22. The apparatus according to the preceding claims, further characterized in that it comprises: one or more additional feeders for feeding the particulate material to the vertical roller mill; wherein one or more additional feeders are each positioned to receive a supply of the particulate material and to direct a flow of that material to the respective grinding zone of a grinding roller.

23. The apparatus according to any of the preceding claims, further characterized in that the grinding table and the grinding rollers of the vertical roller mill are fixed relative to each other during operation except for rotation at a predetermined adjustable distance, thereby creating a fixed grinding zone.

24. The apparatus according to any of the preceding claims, further characterized in that the vertical roller mill further comprises a support device for the inner grinding zone extending axially away from the grinding table, beyond the grinding surface of the grinding table, being substantially concentric with the axis of rotation of the grinding table and having an outer diameter equal to 0.8 to 1.0 times the inner diameter of the grinding surface of the grinding table.

25. The apparatus according to any of the preceding claims, further characterized in that the vertical roller mill further comprises at least one outer grinding zone support device extending radially beyond the grinding surface of the grinding roller, having a surface facing the grinding table, said surface being axially located at a distance from the axis of rotation of the grinding table of 1.0 to 1.1 times the outer radius of the grinding surface of the grinding table measured in a plane coincident with the grinding surface of the grinding table and perpendicular to the axis of rotation of the grinding table, such that the surface of the outer grinding zone support device facing the grinding table provides lateral support for the flow of material in the grinding zone and thereby reduces lateral spillage of material.

26. The apparatus according to any of the preceding claims, further characterized in that it is configured to be operable at a speed by giving the grinding surface of the grinding roller a tangential speed of at least 2 m / s or at least 4, 6, 8, 10, 12, 14, 16, 19, 22, or 25 m / s.

27. The apparatus according to any of the preceding claims, further characterized in that the particulate material is selected from mined minerals, industrial minerals and chemicals, sand, slag, ash, clay, coating pigments, pharmaceuticals and cement raw materials, in particular for cement production.

28. A method for grinding particulate material, characterized in that it comprises: receiving a supply of particulate material; forming a flow of the particulate material; using a feeder to direct the flow of particulate material to a grinding zone of a vertical roller mill comprising a grinding table and a grinding roller having an axis of rotation, each table and roller having a grinding surface and being arranged to define said grinding zone between the grinding surfaces of the grinding roller and the grinding table, the grinding roller being arranged to roll over the particulate material in a grinding path on said grinding table, at a speed relative to the axis of the grinding roller of at least 0.3 times the tangential speed of the grinding surface of the grinding roller or at least 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 2.0, 3.0 or 4.0 times the tangential speed of the grinding surface of the grinding roller; and grind the material into particles in the vertical roller mill.

29. The method according to claim 28, further characterized in that it comprises the feeder that directs the flow of material towards the grinding zone at substantially the same speed relative to the axis of the grinding roll as the tangential speed of the grinding roll in the grinding zone.

30. The method according to claim 28 or 29, further characterized in that it comprises directing the particulate material to the grinding zone of the vertical roller mill in a substantially straight direction, i.e., without substantial directional change between the feeder and the grinding zone other than that caused by gravity.

31. The method according to claim 28, 29 or 30, further characterized in that it comprises compacting the material flow by imposing a change of direction by applying a centrifugal force.

32. The method according to claims 28 to 31, further characterized in that it comprises directing the particulate material to the grinding zone at a speed relative to the axis of the grinding roll of at least 0.6 times the tangential speed of the grinding surface of the grinding roll or at least 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or 2.0 times the tangential speed of the grinding surface of the grinding roll.

33. The method according to any of claims 28 to 32, further characterized in that it further comprises providing an airflow substantially parallel to and in contact with the flow of the material being transferred and characterized in that the airflow has a velocity between 0.5 and 3 times the velocity of the flow of the particulate material, such as at least 0.5 times the velocity of the material or at least 0.6, 0.8, 1.0, 1.2, 1.4 or 2.0 times the velocity of the material.

34. The method according to any of claims 28 to 33, further characterized in that forming a particulate material flow comprises combining several material flows to provide a common material flow.

35. The method according to any of claims 28 to 34, further characterized in that it further comprises supporting the particulate material in the grinding zone at least on one side of the grinding zone to reduce the escape of the particulate material from the volume between the grinding surfaces.

36. The method according to any of claims 28 to 35, further characterized in that the particulate material is selected from mined minerals, industrial minerals and chemicals, sand, slag, ash, clay, coating pigments, pharmaceuticals and cement raw materials, in particular for cement production.

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