EP4121211A1

EP4121211A1 - Device and method for grinding material, in particular material made of thermoplastics and/or elastomers

Info

Publication number: EP4121211A1
Application number: EP21715494.7A
Authority: EP
Inventors: Holger Hannemann
Original assignee: Boilesen Hansen Birgit
Current assignee: Boilesen Hansen Birgit
Priority date: 2020-03-19
Filing date: 2021-03-19
Publication date: 2023-01-25
Anticipated expiration: 2041-03-19
Also published as: DE102020107642A1; EP4121211C0; WO2021186020A1; DE102020107642B4; EP4121211B1

Abstract

The invention relates to a grinding device (1b) for grinding material (3), comprising a cooling assembly (6) with liquid nitrogen (LN) for cooling supplied material (3) and an impact mill (4), which is arranged downstream of the cooling assembly (6), for grinding the cooled material (3) to form fine material (9), the impact mill (4) having at least one connection (4b) for supplying both the cooled material (3) and a nitrogen stream (20) of gaseous nitrogen (GN) into the impact mill (4), and a fine-material outlet (4c) for discharging the fine material (9) produced in the impact mill (4). According to invention, at least one pre-cooling assembly (16) is present, wherein provided material (3) may be pre-cooled by the at least one pre-cooling assembly (16) to a material intermediate temperature (TZ3), the at least one pre-cooling assembly (16) being arranged upstream of the cooling assembly (6) in such a way that the material (3) pre-cooled to the material intermediate temperature (TZ3) by the at least one pre-cooling assembly (16) may pass into the liquid nitrogen stream (LN) after having been supplied into the cooling assembly (6). A mixing cell is also provided, which is designed to provide the nitrogen stream of gaseous nitrogen at a predefined nitrogen stream target temperature and a predefined nitrogen stream target throughput and to supply it to the connection of the impact mill to reproducibly achieve a high degree of fineness of the discharged fine material (9).

Description

Device and method for grinding regrind, in particular made of thermoplastics and / or elastomers

The invention relates to a device and a method for Vermah len of regrind, in particular made of thermoplastics and / or elastomers, in particular rubber waste, such as old tires.

It is known to embrittle rubber waste, such as rubber granulate from old tires, in a cooling unit, such as a vortex screw cooler, with the addition of liquid nitrogen and then in an impact mill, for example a disintegrator with counter-rotating rotor disks equipped with beater elements, as regrind grind. As a result, ground rubber particles with a grain size range from Opm to 800pm can be produced. This is described by way of example in DE 102 46 240 B4, DE 43 22 757 C1 or DD 309644 1.

The mode of operation of a disintegrator is based on impact and impact comminution by means of concentrically arranged, interlocking impact element formations on counter-rotating rotor disks. The shredding work is done by the impact of the impact elements and mutual particle collisions. The ground material arriving through pneumatic transport is pre-shredded centrally on the axis by a first formation of impact elements and then inevitably passes through the following arrangement of impact element rings. The desired properties of the ground material, such as the fineness, can be decisively influenced by changing the rotor speed, the geometry or the number of hammer elements. Alternatively, pin mills, eddy current mills, Luftwirbelmüh len or the like. Can be used in which the comminution of the ground material is also achieved by impact-impact stress.

The disadvantage of previous methods is that they do not contain the desired proportion of fine-grain rubber particles. This follows in particular from the fact that the ground material in the previous grinding processes can only be cooled uniformly with difficulty due to its thermal properties. For example, an object made of rubber can generally be more difficult to cool inside than on its surface, so that a very long cooling section in the vortex screw would be necessary for even cooling, but this makes little sense from an economic and structural point of view. In previous processes, a disproportionately high consumption of liquid nitrogen (LN) is registered to partially compensate for this disadvantage. Nevertheless, the brittleness of the ground material is not evenly distributed in previous grinding processes, so that the object breaks more heavily inside than on its surface. For this reason alone, the embrittlement of the ground material cannot be optimally achieved in previous cooling processes, which has direct effects on the degree of fineness of the ground rubber particles.

Previous grinding processes also assume that the material to be ground and the respective high-speed impact mills are to be kept as cold as possible in order to ensure the embrittlement state in order to achieve the highest possible degree of fineness. Therefore, a large amount of liquid stick is added to the grist in the cooling phase in the vortex screw cooler and the grist is fed into the impact mill together with the then gaseous nitrogen. The degree of fineness to be achieved in an impact mill that works in this way, for example a disintegrator, also depends on how the flow of milled material from the milled material and the gaseous nitrogen with the different ratios the positioned impact elements interacts or how much energy is exchanged between the flow of grist and the correspondingly shaped and specifically arranged impact elements when the rotor disks move at defined rotational speeds.

Previous methods for grinding regrind do not take into account that in order to optimize the degree of fineness, in addition to the shape, the arrangement and the number of striking elements and the rotational speeds of the red disks, not only the temperature of the stream of regrind is decisive, but also the Density of the supplied grist flow, as this also has a significant influence on the grinding process in the impact mill.

The object of the invention is therefore to provide a grinding device and a method that enables grinding of ground material, in particular thermoplastics and / or elastomers, in a simple and efficient manner, in order to increase the degree of fineness while simultaneously optimizing the consumption of liquid nitrogen and drive energy raise.

This object is achieved by a grinding device and a method according to the independent claims. Preferred developments are specified in the subclaims.

The generic assumption here is a grinding device which has a cooling unit with liquid nitrogen for cooling the ground material supplied to a grinding material starting temperature and an impact mill, for example a disintegrator, which is indirectly connected downstream of the cooling unit, for grinding the grind cooled to the grinding material starting temperature has good to fine goods. In this context, regrind is understood to mean in particular an elastic to viscoplastic substance which, under normal temperatures or without cooling or embrittlement, does not effectively crushed in an impact mill. Such a grist can be, for example, wax, rubber, a thermoplastic, an elastomer or a substance with comparable properties.

In the context of the invention, an impact mill is understood to mean a mill in which the comminution of the material to be ground is achieved by impact-impact stress. In the event of an impact load, the abandoned grist is hit by a fast-moving impact element and crushed by impact. In the event of an impact load, the rapidly accelerated grist hits a stationary or otherwise accelerated surface (impact element, other particles) and is crushed by impact (impact). Such impact mills are, for example, high-speed disintegrators, pin mills, eddy current mills, Luftwir belmühlen or the like.

The impact mill has at least one connection for feeding the ground material cooled to the ground material starting temperature and a nitrogen stream of gaseous nitrogen into the impact mill and a fine material outlet for discharging the fine material produced in the impact mill. In the impact mill there is therefore a mixture of ground material and gaseous nitrogen, a flow of ground material, the nature of which is to be optimized according to the invention, in particular with regard to its density.

According to the invention it is provided that the grinding device furthermore has a mixing cell, the mixing cell being designed to provide a nitrogen flow of gaseous nitrogen with a predetermined nitrogen flow target temperature and a predetermined nitrogen flow target throughput and to condition or control this A tempered and metered nitrogen flow is fed to the connection of the impact mill. As a result, a grist flow density of the grist flow in the impact mill can advantageously be optimized, thereby increasing the degree of fineness of the discharged fine material can be improved while optimizing the consumption of drive energy of the impact mill and nitrogen, and reproducibly higher degrees of fineness can be achieved with the nitrogen flow target temperature and nitrogen flow target throughput appropriately adapted to the design of the impact mill.

This follows from the fact that the thus optimized grinding material flow in a high-speed impact mill interacts with the striking elements depending on the number, selected shape or arrangement of the striking elements and the set rotational speeds of the rotor disks, which results in a certain amount of heat being generated. This heat input warms up the grist flow, which, if the wrong operating parameters are selected, means that the grist loses its state of embrittlement, i.e. at least partially returns to its elastic state, so that the desired degree of fineness can no longer be achieved during grinding.

It is therefore necessary to ensure that the cold energy stored in the cooled grist stream is just sufficiently dimensioned to compensate for the heat generated in the impact mill by the energy exchange, which is dependent on the design of the impact mill, and to completely compensate for the grist as a result To keep the embrittlement state. The construction of the impact mill and the nature of the grist stream, in particular its grist stream density, which also changes during the grinding process due to the development of heat, must therefore be coordinated with one another in a targeted manner for optimal operation. The nature of the grinding material flow can be influenced by the mixing cell according to the invention, which is able to provide a nitrogen flow with a correspondingly predetermined nitrogen flow target throughput and a predetermined nitrogen flow target temperature, so that at least at the entrance of the impact mill can set a grist flow density with which in the correspondingly designed impact mill enables optimized operation.

Preferably, it can be provided that the nitrogen flow target temperature and the nitrogen flow target throughput of the nitrogen flow supplied to the impact mill depending on the construction of the impact mill, in particular depending on an arrangement, number and shape of the beaters and the set Rotational speeds of the rotor disks on which these striking elements are located, and / or in dependence from the abandoned grist, in particular a spec. Heat capacity of the ground material, is given. As a result, an optimal grist flow density and, accordingly, an optimized operation of the impact mill or the grinding device with a high degree of fineness can be achieved reproducibly for each impact mill and for each grinding material.

In order to ensure that the respective impact mill is already supplied with a deep-cold grinding stock of preferably -196 ° C, ie cooled to the temperature of liquid nitrogen, the grinding device has at least one pre-cooling unit for pre-cooling the supplied grinding well on an intermediate grinding stock Temperature, preferably in countercurrent with the aid of gaseous nitrogen, the at least one pre-cooling unit being connected upstream of the cooling unit in such a way that the regrind, which has been pre-cooled to the intermediate regrind temperature by the at least one pre-cooling unit, directly or indirectly after being fed into the cooling unit get into the liquid nitrogen and immerse in it. The cooling unit preferably has a tank, the tank being fillable with the liquid nitrogen up to a fill level limit in order to cool the regrind located therein to a defined regrind starting temperature of up to approx. -196 ° C. This already has the advantage that the millbase is cooled over a long period of time by at least one pre-cooling, which is preferably carried out in countercurrent only via gaseous nitrogen, and by main cooling, which is carried out exclusively via nitrogen in liquid form. Since the liquid nitrogen acts on the ground material in a tank and the pre-cooled ground material is preferably removed from the tank on the underside, the ground material can be cooled efficiently and with a long dwell time in the tank and thus effectively embrittled. This gives the regrind the possibility that it is evenly cooled down into the interior or down to the core. As a result, the grist can keep its temperature at a low level for longer, so that a low initial fines temperature can still be maintained until after the grinding process. As a result, the ground material can still remain in its embrittlement state during the entire grinding process.

The pre-cooling and the main cooling have an overall positive effect on the grinding process in the impact mill, since the material is more brittle overall or has an almost uniform brittleness due to the long residence time in a cold environment. As a result, the material in the impact mill breaks better overall, which has a positive effect on the degree of fineness of the fine material.

A locally and thermally decoupled supply of the substances participating in the grinding process in the impact mill, cooled ground material and gaseous nitrogen or nitrogen flow for inerting and ensuring a brittle fracture can advantageously also take place.

In the context of the invention, such a decoupled supply is to be understood as meaning that the substances are initially metered individually and independently of one another in a spatially separate manner and are individually tempered and the impact mill can then be fed individually or together in order to interact as a stream of material to be ground together with the impact elements of the impact mill. The feeding into the impact mill does not necessarily have to take place separately. Rather, the two substances, which are independently dosed and individually tempered, can already be brought together via a Y-piece in front of the impact mill, for example, and fed together as a mixture (grist flow) via the connection into the impact mill.

In the procedure in the prior art, the substances participating in the grinding process in the impact mill, ground material and gaseous nitrogen, are kept at approximately the same temperature in the upstream cooling process and then fed into the impact mill. This makes it impossible to set the optimum grist flow density in the impact mill and thus to optimize the degree of fineness of the discharged fine material while at the same time optimizing the consumption of drive energy of the impact mill and nitrogen. The aim of keeping the ground material in its embrittlement state even during the entire grinding process and thus ensuring brittle fracture is therefore not at least economically feasible in the prior art.

In the case of the grinding device according to the invention, it is preferably also provided that the mixing cell has a plurality of inflows and an outflow, the mixing cell via the plurality of inflows, for example

- Gaseous nitrogen from a nitrogen gas generator and / or residual gas from a pneumatic filter, i.e. from the grinding process, and / or a pre-cooling gas flow from the at least one pre-cooling unit and / or

- liquid nitrogen can be supplied from a nitrogen tank.

A wide variety of nitrogen sources can thus be used in order to set the corresponding predetermined throughput or the predetermined temperature of the nitrogen flow, which makes the process more flexible will. Instead of or in addition to the nitrogen sources mentioned, further nitrogen sources can also be provided. Depending on the construction of the grinding device and the specification of the target values, the already existing pre-cooling gas flow or the residual nitrogen gas from the grinding process can be used, or else gaseous nitrogen can be specifically generated with a nitrogen gas generator or liquid nitrogen from a nitrogen gas generator. Tank are provided in order to provide the predetermined amount of nitrogen and / or to achieve a corresponding temperature control.

Preferably, it is further provided that the mixing cell also has a mixing chamber, wherein the gaseous nitrogen supplied via the multiple inflows and the liquid nitrogen evaporating in the mixing chamber can be mixed in the mixing chamber in such a way on a heat exchange path that the outflow connected to the Connection of the impact mill is connected or connectable, forms a nitrogen flow with the predetermined nitrogen flow target temperature and the predetermined nitrogen flow target throughput. As a result, the nitrogen flow can be conditioned in a simple manner in the mixing chamber from the different inflows. In order to increase a heat exchange path within the mixing chamber, channels arranged in a meandering pattern, for example formed by nested tubes, can be provided in the mixing chamber, within which the supplied gaseous nitrogen from the individual inflows is guided to the outflow with mutual mixing.

Preferably, it is additionally provided that at least each inflow through which gaseous nitrogen is introduced into the mixing chamber is assigned a sensor system, the sensor system being designed to provide an actual mass flow and / or an actual temperature of at least the gaseous nitrogen in the respective Record inflow. This enables the deployment a predetermined conditioned (metering and temperature control) nitrogen flow through the mixing cell can be carried out more precisely and faster. In addition, a sensor system is preferably also provided at the outlet of the mixing cell in order to enable a target / actual comparison of the outgoing conditioned nitrogen flow. It can also be determined, for example, whether more or less liquid nitrogen is to be fed into the mixing chamber via the respective inflow in order to reduce or increase the nitrogen flow temperature and thus adapt it to the nitrogen flow target temperature.

Preferably, it is additionally provided that at least some of the inflows are assigned an inlet valve, the respective inlet valve being designed to enable or prevent a supply of gaseous nitrogen and / or liquid nitrogen via the respective inflow into the mixing chamber. A throttle valve is preferably provided as the inlet valve, the throttle cross-section of which can be set in fine steps in order to regulate the respective incoming mass flow. The dosing of the individual nitrogen sources can therefore be controlled in a simple and fine-grained manner. In order to prevent backflow from the mixing chamber to the individual stick material sources, check valves can also be provided for each inflow. Such a non-return valve can also be provided in the drain in order to prevent the grinding material flow from flowing back into the mixing chamber of the mixing cell in the event of an undesired pressure increase, e.g. in the impact mill.

It is preferably also provided that the mixing cell has a mixing cell control device, the mixing cell control device being designed, for example via a corresponding algorithm, to control the inlet valve of the respective inflow, preferably based on the values measured by the sensors, so that the mixing chamber becomes more gaseous Nitrogen and / or liquid nitrogen is supplied and mixed therein via the heat exchange path in such a way that a nitrogen flow with the specified nitrogen flow target temperature and the specified nitrogen flow target throughput is formed at the outlet of the mixing cell. This enables the setting of an optimized nitrogen flow or an optimized grist flow density in a simple manner by a corresponding electrical control based on the values measured by the sensors, so that a reproducible provision of fine material with a high degree of fineness can be achieved.

The design of the at least one pre-cooling unit is variable and can be selected, for example, depending on the location and application. For example, at least one countercurrent pre-cooling unit, each with a pre-cooling section and / or at least one container pre-cooling unit with a container interior, can be provided as the pre-cooling unit. In this case, the at least one countercurrent pre-cooling unit is designed to pre-cool existing or transported material to be ground in the at least one countercurrent pre-cooling unit in a countercurrent of gaseous nitrogen within the respective pre-cooling section. In this context, countercurrent is understood to mean that the conveying direction of the ground material is oriented opposite to the conveying direction of the gaseous nitrogen. The Behäl ter pre-cooling unit, for example a refrigerated container, is designed to pre-cool any ground material located in the container interior, for example according to the Linde process.

It is preferably provided that the at least one countercurrent pre-cooling unit is connected upstream of the cooling unit in such a way that a pre-cooling gas stream formed in the cooling unit by evaporation of the liquid nitrogen can be introduced into the at least one counter-current pre-cooling unit in order to Pre-cooling unit located regrind within the respective pre-cooling section to precool in a countercurrent through the precooling gas flow to an intermediate millbase temperature. Depending on the design of the pre-cooling section at the transition to the Kühlaggre gat, the regrind intermediate temperature should roughly correspond to the nitrogen intermediate temperature of the pre-cooling gas flow, after the pre-cooling gas flow has passed all countercurrent pre-cooling units, with temperatures of example wisely less than approx. -40 ° C can prevail.

As a result, the nitrogen, which is already evaporating in the cooling unit, can be used as a countercurrent for the pre-cooling of the ground stock, so that no further substances or cooling elements are required for the pre-cooling in the at least one countercurrent pre-cooling unit. The warmer grist, which is immersed in the liquid nitrogen of the cooling unit, automatically evaporates the liquid nitrogen and thus provides a precooling gas flow that can be used for precooling.

It is also preferably provided that the at least one countercurrent pre-cooling unit is arranged above the cooling unit, so that the pre-cooling gas flow formed by evaporation of the liquid nitrogen can reach the respective pre-cooling section of the respective counter-current pre-cooling unit as a chimney-like countercurrent. Accordingly, no additional gas lines or gas ducts are necessary in order to conduct the gaseous nitrogen for pre-cooling from the cooling unit into the respective countercurrent pre-cooling unit.

Advantageously, however, conveying paths between the at least one countercurrent precooling unit and the main cooling unit for the precooled ground material can also be dispensed with if a first countercurrent precooling unit is used as the at least one countercurrent precooling unit, which is designed in this way and is connected directly or indirectly upstream of the cooling unit that the first countercurrent pre-cooling unit supplied grinding stock can fall due to gravity along a first pre-cooling section of the first countercurrent pre-cooling unit and the falling material to be guided can be pre-cooled at the same time in a countercurrent of gaseous nitrogen, preferably the pre-cooling gas stream, within the first pre-cooling section and then into the liquid Nitrogen from the tank.

Compared to an arrangement of the first countercurrent pre-cooling unit, e.g. below or next to the cooling unit, increased conveying expenditure, insulation expenditure and costs can be avoided. At the same time, the precooling gas flow can rise against the direction of fall of the ground material caused by gravity upwards out of the cooling unit into the first countercurrent precooling unit in order to generate a countercurrent. This simplifies pre-cooling and feeding the ground material into the cooling unit.

The first countercurrent pre-cooling unit of the pre-cooling and the cooling unit of the main cooling can be designed as separate system parts of the grinding device or can be summarized in one component. It is only necessary to ensure that the evaporating nitrogen from the cooling unit can be guided as completely as possible into the first countercurrent pre-cooling unit in order to be able to provide for pre-cooling of the ground material in countercurrent.

The first pre-cooling section in the first countercurrent pre-cooling unit and possibly also further pre-cooling sections in further counter-current pre-cooling units must be adapted in such a way that a comprehensive energy exchange can take place in the countercurrent between the vaporizing gaseous nitrogen of the pre-cooling gas flow and the ground material supplied. At a certain throughput of ground material fed in, the amount of evaporating nitrogen in the pre-cooling gas flow decreases after the start-up. After a certain period of time, the system will reach a certain state of equilibrium. With ideal coordination of the respective pre-cooling section, an efficient energy exchange takes place in this equilibrium state, on the basis of which the intermediate grist temperature and the intermediate nitrogen temperature at the corresponding points (see above) approximately equalize, for example at about -40 ° C or less.

According to a further embodiment for the pre-cooling, a second countercurrent pre-cooling unit can be provided, which is designed and connected directly or indirectly upstream of the cooling unit in such a way that the ground material fed to the second counter-current pre-cooling unit is transported in a vortex screw interior along a second pre-cooling section can and the supplied grinding stock can be simultaneously precooled in a countercurrent of gaseous nitrogen, preferably the precooling gas flow, within the second precooling section while mixing with the gaseous nitrogen.

By using a vortex screw, an effective thermal exchange of energy between the gaseous nitrogen and the ground material can take place, since the vortex screw creates turbulent instead of laminar flow conditions and the two substances are better mixed with each other and can interact thermally, so that an efficient Pre-cooling can be done. This can be done in addition to or instead of the first countercurrent pre-cooling unit, so that the process can be designed flexibly as a whole.

In this embodiment, too, a corresponding arrangement of the second countercurrent pre-cooling unit allows a pre-cooling gas flow formed in the cooling unit by evaporation of the liquid nitrogen to enter the vortex screw interior of the second countercurrent pre-cooling unit, through which the grinding stock is caused by the rotation of the vortex screw is transported. The precooling gas flow can therefore additionally, after it has possibly passed the precooling section in the first countercurrent precooling unit, ensure countercurrent precooling in the second countercurrent precooling unit. Optionally, depending on the coordination of the grinding process, liquid nitrogen can be let into the interior of the vortex screw at least temporarily.

It is preferably also provided that a third countercurrent pre-cooling unit is formed by a feed silo, the feed besilo providing ground material for the grinding process, whereby gaseous nitrogen, for example residual gas from a pneumatic filter, can be introduced into the feed silo in such a way that the feed silo therein Grist located within a third pre-cooling section can be precooled in countercurrent from gaseous nitrogen before the grist is discharged from the feed silo.

This means that pre-cooling can advantageously take place in the feed silo in order to support the pre-cooling process. For this purpose, for example, residual nitrogen gas in the process from a pneumatic filter of the grinding device can be used.

If a container pre-cooling unit is also used, which is arranged in front of the feed silo, for example, the ground material is located for pre-cooling within a container interior of the container pre-cooling unit, the container interior, for example, to less than -10 ° C, preferably less than -30 ° C, in particular down to -70 ° C, is cooled, for example, according to the Linde method and possibly with the support of residual nitrogen gas in the process from a pneumatic filter of the grinding device. The ground material located in the interior of the container is then fed to the one or more countercurrent precooling unit (s) already precooled. In order to enable efficient countercurrent precooling, at least one countercurrent precooling unit, in particular the first countercurrent precooling unit, is preferably to be provided in front of the main cooling unit. As a result, depending on the application and location of the grinding device, an alternative or further, possibly more energy-efficient, precooling can be made possible.

It is also preferably provided that the at least one countercurrent pre-cooling unit is preceded by a metering screw, the metering screw metering the ground material provided from a feed silo and / or from a Siebvor direction (as a return of coarse grain) and / or from the container pre-cooling unit into the at least one countercurrent pre-cooling unit conducts. Accordingly, the speed or the feed rate of the material to be ground can be set in a targeted manner via the metering screw, for example as a function of the pre-cooling gas flow generated, in order to control the cooling and grinding process in a targeted manner.

It is also preferably provided that a screw conveyor, preferably a motor-driven screw conveyor, is connected downstream of the cooling unit, the screw conveyor dosing the ground material cooled to the starting material temperature, i.e. conveying it with a defined mass flow to at least one connection of the impact mill. This means that the material to be ground fed to the impact mill can also be dosed in order to make the grinding in the impact mill efficient.

It is preferably also provided that the ground material and / or the fine material are kept inert within the entire grinding device.

This advantageously ensures that the entire process is not adversely affected by migration of oxygen and air humidity from the ambient air. This can be achieved by appropriately closed system parts in which gaseous nitrogen and / or excess pressure is located. In addition, it can be provided that at least when switching off the grinding device via the mixing cell by opening the respective inlet valve accordingly, gaseous nitrogen, which is provided by the stick material gas generator, is conveyed into the circuit.

As a result, the nitrogen gas generator, which is connected to the mixing cell, can also prevent humid ambient air from entering the circuit when the system is switched off.

According to the invention, a method for grinding grinding well, preferably made of thermoplastics and / or elastomers, in particular with a grinding device according to the invention, with at least the following steps is provided:

- Provision of regrind and feeding the regrind into at least one pre-cooling unit for pre-cooling the supplied regrind, preferably in countercurrent, to an intermediate regrind temperature;

- Feeding of the pre-cooled to the intermediate grinding stock temperature into a cooling unit with liquid nitrogen, so that the pre-cooled grinding stock is cooled by the liquid nitrogen to a starting temperature for the grinding stock;

- Conveying the ground material cooled to the initial grinding material temperature into an impact mill;

- Grinding of the ground material cooled to the initial grinding material temperature into fine material with simultaneous supply of a nitrogen stream of gaseous nitrogen, the nitrogen stream of gaseous nitrogen being provided to the impact mill with a predetermined nitrogen stream target temperature and a predetermined nitrogen stream target throughput in order to provide the impact mill with a defined grist stream density of a grist stream composed of the grist and the nitrogen stream.

As already described, the pre-cooling and cooling in the bath of liquid stick means that the grist is efficiently absorbed into the interior A low grinding stock initial temperature is cooled before it reaches the impact mill with a defined mass flow and is ground together there with a correspondingly conditioned nitrogen flow, so that the grinding process can be made more efficient overall and, depending on the application, higher degrees of fineness can be achieved reproducibly.

It is preferably also provided that the provision of the cooled ground material in the impact mill is thermally decoupled from the provision of the nitrogen flow from gaseous nitrogen before these are fed to the impact mill. As a result, the impact mill or the grinding device can be operated more efficiently overall, as already described be.

The invention is tert erläu below with reference to drawings. Show it:

1 shows a grinding device according to the prior art;

Fig. 2 shows a first embodiment of a grinding device according to the invention;

Fig. 3 shows a second embodiment of a grinding device according to the invention; and

4a, 4b are perspective views of a mixing cell.

Fig. 1 shows schematically a grinding device 1a according to the prior art, which serves to feed in a feed silo 2 via a lower feed silo opening 2a grist 3 by an impact mill 4, for example a disintegrator 4a, in a certain degree of fineness to grind. On the way to the impact mill 4, the grist 3 is dosed accordingly via a dosing screw 5 and passed with a grist input temperature TE3 of, for example, 20 ° C in a cooling unit 6, vorzugswei se a motorized vortex screw cooler 6a.

Via a nitrogen inlet 7, liquid nitrogen LN from a nitrogen tank 35 with a nitrogen-liquid temperature TLN of approx to cool the conveyed grist 3 and thus become brittle. From the outlet 8 of the eddy screw cooler 6a, the grist 3, cooled by the liquid nitrogen LN to a grist starting temperature TA3, and the evaporation nitrogen gas at approximately the same temperature pass through a connection 4b into the impact mill 4 or the disintegrator 4a and is milled therein in a cooled form in an inert atmosphere. The regrind starting temperature TA3 of the regrind 3 can be approx. -150 ° C.

In addition, a further nitrogen stream 20 can be fed to the disintegrator 4a via the connection 4b, so that in the disintegrator 4a there is a mixture (regrind stream 30) of regrind 3, nitrogen gas created by evaporation for inerting and the nitrogen stream 20 that may be additionally supplied , this grinding stock flow 30 having a certain grinding stock flow density Rho at connection 4b, which changes during the grinding process due to the development of heat. The optional nitrogen stream 20 serves to support the pneumatic conveyance of the ground material mixed with gaseous nitrogen GN or the fine material 9 produced in the impact mill 4 and mixed with gaseous nitrogen GN. From the impact mill 4, a fine material stream 90 produced therein is discharged from fine material 9 mixed with gaseous nitrogen GN with a fine material output temperature TA9 of, for example, approx. -20 ° C. via a fine material output 4c. When the disintegrator 4a is operating, the nitrogen stream 20 automatically ensures that the fine material stream 90 (fine material 9 mixed with gaseous nitrogen GN) is pressed out of the fine material outlet 4c, so that the fine material stream 90 is pneumatically conveyed to the next element of the grinding device 1a, here a cyclone 10, is made possible. The pneumatic transport of the fine material stream 90 to the cyclone 10 is supported by a fan 15.

Subsequently, the fine material stream 90 arrives in a cyclone 10, in which most of the fine material 9 is separated from the fine material stream 90 from the gaseous nitrogen GN, with the fine material 9, for example rubber powder, then being discharged from the cyclone 10. This fine material 9 is then passed in possibly warmed up form into a screening device 12, in which it is separated into its different fine material fractions, ie coarse grain 11 G and fine grain 11 F (depending on the later use via the appropriate screen cuts to be selected) . The coarse grain 11 G of the fine material 9 can optionally be conveyed back to the metering screw 5 in any way, e.g. via a repassing line 24 and thus fed back into the grinding process. The fine grain 11 F has, for example, a grain spectrum of <200 μm and can be used accordingly as finished product 13.

The remaining part of the fines stream 90 in the cyclone 10, which in particular consists of gaseous nitrogen GN and fines 11 S, is separated into its components in a pneumatic filter 14. Since be already a separation has taken place in the cyclone 10, the pneumatic cal filter 14 is used for the residual separation of fine material 11 S and gaseous Nitrogen GN is less heavily loaded and can therefore be dimensioned correspondingly small.

The fine material dust 11 S is also fed into the sieve device 12 in a warmed-up form, if necessary. A fan 15 is provided for conveying the cold gaseous nitrogen GN and the fine material dust 11 S from the cyclone 10 into the pneumatic filter 14. This sucks in the remaining fine material stream 90 of gaseous nitrogen GN and the fine material dusts 11 S from the cyclone 10 and blows the filtered gaseous nitrogen GN as a cold nitrogen stream 20 to support the pneumatic transport to the connection 4b back to the impact mill 4.

In order to optimize the grinding process, individual changes are provided in the grinding device 1b according to the invention as shown in FIGS. 2 and 3. The same designations and reference symbols are used below for components that have the same effect as the prior art (FIG. 1).

Accordingly, it is provided in Fig. 2 that in a feed silo 2 via the lower feed silo opening 2a fed regrind 3 appropriately dosed via a metering screw 5 and with a regrind inlet temperature TE3 in a first countercurrent pre-cooling unit 16a and from this in the actual cooling unit 6 is passed. The first countercurrent pre-cooling unit 16a serves to pre-cool the ground material 3 to an intermediate ground material temperature TZ3 of between -35 ° C. and -45 ° C., for example. This intermediate millbase temperature TZ3 is at an ideal temperature at the lower end of the first countercurrent pre-cooling unit 16a, so that the millbase 3 can pass into the main cooling at this temperature. The ground material 3 located in the first countercurrent pre-cooling unit 16a is pre-cooled by a pre-cooling gas flow 17 of gaseous nitrogen GN directed upward in FIG. 2. This pre-cooling gas flow 17 has an intermediate nitrogen temperature TZN of between -35 ° C. and -45 ° C., at least at the upper end of the first countercurrent pre-cooling unit 16a. The intermediate grist temperature TZ3 and the intermediate nitrogen temperature TZN are set depending on the design and application of the grinding device 1b, but they can also deviate from the values mentioned. Overall, the temperature values mentioned in the exemplary embodiments of the invention, in particular for the gaseous nitrogen GN, the ground material 3 and the fine material 9, are dependent on the design and the application and can therefore also deviate accordingly from the values mentioned.

According to this embodiment, the pre-cooling gas flow 17 acts on the supplied ground material 3 on a certain first pre-cooling section SVa, this being done in a countercurrent, ie the ground material 3 falling down over the first pre-cooling section SVa is replaced by the oppositely directed pre-cooling Gas stream 17 cooled.

According to this embodiment, the pre-cooling gas flow 17 is generated in that liquid nitrogen LN located in the cooling unit 6 evaporates and the resulting gaseous nitrogen GN is passed upwards through the first countercurrent pre-cooling unit 16a like a chimney. The cooling unit 6 and the first countercurrent pre-cooling unit 16a can be designed in one piece or as separate Bauein units, the extent of the first countercurrent pre-cooling unit 16a being determined by the first pre-cooling section SVa. In this respect, the illustration in FIG. 2 is only intended to indicate schematically that there is any transition between the cooling unit 6 and the first countercurrent pre-cooling unit 16a, which is a passage of pre-cooled Grist 3 in the cooling unit 6 and gaseous nitrogen GN in the first countercurrent pre-cooling unit 16a.

According to this exemplary embodiment, the cooling unit 6 is formed by a tank 6b into which liquid nitrogen LN from a nitrogen tank 35 with a nitrogen-liquid temperature TLN of approximately -196 ° C. is admitted via a nitrogen inlet 7 and which is continuously refilled up to a certain level limit 18. Via an upper side 6c of the cooling unit 6 or of the tank 6b, the ground material 3, which has been precooled in the counterflow, is fed to the tank 6b at the intermediate grinding material temperature TZ3 (e.g. -45 ° C). As soon as the pre-cooled regrind 3 reaches the liquid nitrogen LN in the tank 6b, the regrind 3 cools down further and becomes further embrittled. The warmer ground material 3 immersed in the liquid nitrogen LN of the cooling unit 6 leads to the evaporation of the liquid nitrogen LN, so that a precooling gas flow 17 which can be used for precooling is formed.

The first pre-cooling section SVa in the first countercurrent pre-cooling unit 16a is to be adapted in such a way that a comprehensive energy exchange between the gaseous nitrogen GN evaporating in the tank 6b and the ground material passing through the first countercurrent pre-cooling unit 16a is achieved 3 can take place. When the material to be ground 3 is supplied, the amount of evaporating gaseous nitrogen GN of the pre-cooling gas flow 17 after the start-up of the Mahlvor device 1b assumes a state of equilibrium after a certain time. With ideal coordination of the first pre-cooling section SVa, an energy exchange takes place in this equilibrium state, due to which the intermediate grinding temperature TZ3 at the lower end of the first countercurrent pre-cooling unit 16a and the intermediate nitrogen temperature TZN at the upper end of the first Adjust countercurrent pre-cooling unit 16a approximately, for example between -35 ° C and -45 ° C or less. The tank 6b is connected to a motor-operated screw conveyor 19 via an access 6d, which is preferably on the underside. The embrittled grist 3 located in the tank 6b can be conveyed with ideal temperature control with a defined grist output temperature TA3 of approx Connection 4b are fed. Instead of a disintegrator 4a, a pin mill, eddy current mill, air vortex mill, etc., can also be used as the high-speed impact mill 4. In the context of the invention, an impact mill 4 is generally understood to mean a mill in which the crushing of the embrittled material to be ground 3 is achieved by an impact-impact stress. In the event of an impact load, the ground material 3 given is hit by a rapidly moving impact element in the impact mill 4 and crushed by impact. In the event of an impact, the rapidly accelerated grist 3 hits a stationary or otherwise accelerated surface (impact element, other particles) and is crushed by impact (impact).

In the respective impact mill 4, the ground material 3 is then ground in a cooled form in an inert atmosphere. From the impact mill 4, the fine material 9 produced therein is discharged from the fine material output 4c with a fine material output temperature TA9 of, for example, approx or a pneumatic transport of the fine material 9, which is mixed ver with gaseous nitrogen GN to form a fine material stream 90, from the fine material output 4c.

In addition to the grinding stock 3, the respective impact mill 4 or the disintegrator 4a is supplied with a specifically conditioned gaseous nitrogen stream 20 of cold gaseous nitrogen GN with an adjustable Ren nitrogen flow temperature T20 of for example between -75 ° C and -90 ° C and with an adjustable nitrogen flow throughput ND (kg per h). The nitrogen stream 20 serves to inert the atmosphere in the impact mill 4 and to ensure an effective brittle fracture during grinding, as described below. The materials participating in the grinding process, ie the cooled ground material 3 and the gaseous nitrogen GN from the nitrogen flow 20, which together form a ground material flow 30, are supplied in a thermally completely decoupled manner.

A completely decoupled supply means that the substances (3 + 20) are initially metered individually and independently of one another in a targeted manner and individually tempered (TA3, T20) and fed to the impact mill 4 after a metered and individually tempered provision. The introduction of the two substances (3 + 20) into the impact mill 4 is not carried out separately, as shown in FIG. 2. Rather, both substances (3 + 20), which are individually dosed and individually tempered, are brought together, for example via a Y-piece in front of the impact mill 4, and passed together as a mixture or as a grinding material stream 30 via the connection 4b into the impact mill 4.

This distinguishes the embodiment according to the invention in FIG. 2 from the known embodiment in FIG. 1 (state of the art), whereby in FIG reaches the impact mill 4, so that there is no independent metering and no individual temperature control of the substances participating in the grinding process in the impact mill 4, ground material 3 and gaseous nitrogen GN. As a result, the Mahlpro process according to the arrangement of the prior art (Fig. 1) is less effi cient than in the arrangement according to the invention (Fig. 2), as described below: By feeding the nitrogen stream 20 and the precooled ground material 3 into the impact mill 4 in a thermally decoupled manner, a grinding material flow density Rho of the grinding material flow 30 prevailing in the impact mill 4 can advantageously be set lower or in a controlled manner so that the energy consumed to drive the impact mill used 4 decreases or is optimized accordingly and the degree of fineness of the fine material 9 can also be optimized. At the same time, this can also reduce the consumption of nitrogen, so that the grinding process becomes more efficient overall.

This follows from the fact that an impact mill 4 for crushing by impact-impact stress has several impact elements which are fastened to two counter-rotating rotor disks on different orbital radii. Depending on the number, the selected shape or arrangement and the set rotational speeds of the rotor disks, there is an interaction between the striking elements and the supplied regrind stream 30 of regrind 3 and gaseous nitrogen stream 20. Because of this interaction, there is an exchange of energy between the millbase stream 30 and the beater elements, which in turn leads to heat development in the impact mill 4. This heat development is dependent both on the nature of the grinding material flow 30 and on the construction and the operating parameters of the respective impact mill 4.

This heat development also warms the ground material stream 30, which can lead to the ground material 3 losing its state of embrittlement, i.e. at least partially returning to the elastic state, and as a result the desired degree of fineness can no longer be achieved during grinding.

It is therefore necessary to ensure that the cooling energy stored in the cooled grist stream 30 is sufficient to generate the energy used in each case Impact mill 4 to compensate for the heat development caused by the exchange of energy and to keep the grist 3 completely in a state of brittleness. For this purpose, a particularly cold nitrogen stream 20 with a high nitrogen stream throughput ND can be provided, which, however, simultaneously increases the grist stream density Rho in the impact mill 4 so much that both the required drive energy and the heat development in the impact mill 4 increases sharply and the grinding stock 3 loses its state of embrittlement due to the increased heat development.

The nitrogen flow throughput ND and the nitrogen flow temperature T20 of the nitrogen flow 20 are therefore to be set in a targeted manner in such a way that the resulting grist flow density Rho of the grist flow 30 from grinding well 3 and nitrogen flow 20 leads to heat development in the respective impact mill 4 used, which can be compensated for by the stored cold energy in the deeply cold grist stream 30 without the grist 3 losing its state of embrittlement.

When setting the grist flow density Rho of the grist stream 30, it is assumed that the impact mill 4 receives a very cold grist 3 with an optimal grist output temperature TA3 of -196 ° C (temperature of the liquid nitrogen LN) is provided. Since the nitrogen acts longer on the ground material 3 in gaseous form for precooling (in the first countercurrent precooling unit 16a) and in liquid form for main cooling (in cooling unit 6) than in the prior art (FIG. 1), a defined ground material is Output temperature TA3 adjustable from -196 ° C. In addition, the regrind 3 is ideally evenly cooled down to the inside or down to the core, whereby the regrind 3 can keep its temperature at a low level for longer, so that with a correspondingly optimized setting of the regrind flow density Rho, a lower fine material output Temperature TA9 can be reached after the grinding process. The pre-cooling and the main cooling treatment have an overall positive effect on the grinding process in the Prallmüh le 4, since the material is more brittle overall, ie in particular also inside or in the core, or has an almost uniform brittleness and sufficient cold energy can be stored for the grinding process .

In order to obtain a suitably metered and tempered nitrogen stream 20 for the impact mill 4, a mixing cell 21 is provided, which is shown in an exemplary embodiment in FIGS. 4a and 4b. In the mixing cell 21, nitrogen from different independent sources can be mixed with one another in such a way that a nitrogen flow 20 with a nitrogen flow throughput ND (metering) and with a nitrogen flow - temperature T20 (e.g. approx. -87 ° C) (temperature control) is provided, which ideally correspond to a predetermined nitrogen flow target throughput NDS or a predetermined nitrogen flow target temperature TS20. This provision of the nitrogen stream 20 takes place in a targeted manner, thermally decoupled from the provision of the ground material 3.

This specifically metered and tempered nitrogen stream 20 is passed together with the grinding stock 3 via the connection 4b into the impact mill 4, so that a grinding stock flow 30 results, which at the connection 4b has a corresponding grinding stock flow density Rho, which occurs during the grinding process process changes due to the development of heat. The targeted mixing of the nitrogen in the mixing cell 21 provides a nitrogen stream 20 which is conditioned in such a way that the cold energy stored in the cooled grist stream 30 is just sufficiently dimensioned to absorb the heat generated in the impact mill 4 by the energy exchange is dependent on the construction and the operating parameters of the impact mill 4, just to compensate and thereby keep the grist completely in an embrittlement state. At the same time, this also results in an optimized consumption of drive energy for the impact mill 4 and of nitrogen reached and there is sufficient inertization of the ground material 3 in the respective impact mill 4.

The mixing cell 21 is controlled in a targeted manner by a mixing cell control device 21a in order, by specifying a nitrogen flow target throughput NDS or a nitrogen flow target temperature TS20 for the nitrogen flow 20 provided, one for the respective impact mill 4 as well as the ground material 3 to be ground to obtain individually optimized grist stream density Rho of grist stream 30 at connection 4b of impact mill 4. Since impact mills 4, for example disintegrators 4a, can differ in their exact construction, in particular in an order, number and shape of the striking elements and the rotational speeds of the rotor disks on which these striking elements are located, is also that of the grist flow density Rho-dependent heat development in each impact mill 4 different. Furthermore, the properties (specific heat capacity) of the ground material 3 to be ground also have an influence on the grinding process. Therefore, for each impact mill 4 and for each grist 3, a different grist flow density Rho and also a different temperature of the grist stream 30 in the above sense is considered optimal for the operation of the impact mill 4 and the obtained fineness of the fines 9. Therefore, for each impact mill 4 and for each grist 3 a corresponding nitrogen flow target throughput NDS and a corresponding nitrogen flow target temperature TS20 to specify or set for the nitrogen flow 20 in order to ensure optimal operation in this way and a correspondingly high degree of fineness of the Fine goods 9 can be reproduced.

Such an optimized setting can take place by a control or a regulation via the mixing cell control device 21a. For this purpose, the mixing cell 21 has, as shown by way of example in FIGS. 4a, 4b, several inflows 25a, 25b, 25c, 25d, via which a mixing chamber 21b in the Mixing cell 21 gaseous nitrogen GN and / or liquid nitrogen LN can be fed to, wherein the inflows 25a, 25b, 25c, 25d are each connected by lines to corresponding nitrogen sources. In the mixing chamber 21b, for example, by plugging several tubes of different diameters into one another, a heat exchange path 21c with a meandering section can be formed, within which the gaseous nitrogen GN from the individual inflows 25a, 25b, 25c and, if necessary, the liquid nitrogen LN (from 25d) can mix after its evaporation. Due to the meandering shape, the heat exchange path 21c is enlarged compared to an individual chamber, so that effective thermal mixing can take place before the gaseous nitrogen GN leaves the mixing cell 21 as a nitrogen stream 20 via an outlet 28.

The inflows 25a, 25b, 25c, 25d are each inlet valves 26a, 26b, 26c, 26d, for example finely adjustable throttle valves, connected upstream, which can be controlled electrically by the mixing cell control device 21a in order to open or close them. As a result, the supply of the liquid or gaseous nitrogen GN, LN from the respective lines into the mixing chamber 21b can be controlled in a targeted manner. In order to prevent a backflow of nitrogen from the mixing chamber 21b into the individual lines, a check valve is assigned to each inflow 25a, 25b, 25c, 25d. The mixing cell 21 also has the outlet 28, via which the mixture of liquid and / or gaseous nitrogen LN, GN conditioned in the mixing chamber 21b can be fed to the impact mill 4 as a nitrogen stream 20. The outflow 28 likewise has a check valve in order to prevent the nitrogen stream 20 from flowing back, for example in the event of a corresponding overpressure in the impact mill 4.

The inflows 25a, 25b, 25c, 25d are connected according to the embodiment described (see. Fig. 2, 3) with the following nitrogen sources via ent speaking lines. First of all, a first inflow 25a with a ner line to the first countercurrent pre-cooling unit 16a (see Fig. 2) and / or to a second countercurrent pre-cooling unit 16b (see Fig. 3) connected, the first inflow 25a via this line by a finely tuned automatic control of the first inlet valve 26a based on the signals of an upstream sensor system 40a to which the pre-cooling gas flow 17 (TZN, for example approx. -40 ° C.) can be supplied from the respective pre-cooling. In normal operation, such an amount of gaseous nitrogen GN is passed through the respective countercurrent pre-cooling unit 16a, 16b and, after pre-cooling of the ground material 3, is supplied to the first inflow 25a of the mixing cell 21 that the first inlet valve 26a can be opened 100% in order to to avoid the formation of an overpressure in front of the first inflow 25a of the mixing cell 21.

Furthermore, a second inflow 25b is provided, which is connected to the blower 15 via a line, so that the second inflow 25b receives the remaining residual gas R via this line by means of a finely stepped automatic control of the second inlet valve 26b based on the signals of an upstream sensor system 40b (eg approx. -50 ° C) can be fed out of the grinding process. Furthermore, a third inflow 25c is provided, which is connected to a nitrogen gas generator 22 via a line, so that the third inflow 25c is additionally generated via this line by a finely stepped automatic regulation of the third inlet valve 26c based on the signals of an upstream sensor 40c gaseous nitrogen GN can be supplied. Furthermore, a fourth inflow 25d can be connected to the nitrogen tank 35 via a line, so that the fourth inflow 25d can be supplied with liquid nitrogen via this line by finely stepped automatic regulation of the fourth inlet valve 26d based on the signals of a sensor system 40 located in the outflow 28 LN (TLN approx. -196 ° C) can be supplied. At least the inflows 25a, 25b, 25c, through which the gaseous stick material GN is passed into the mixing chamber 21b, are each assigned a sensor system 40a, 40b, 40c, which is designed to provide an actual mass flow MFa, MFb, MFc and an actual -Temperature Tla, Tlb, Tic of the stream of gaseous nitrogen GN arriving in the respective inflow 25a, 25b, 25c to be determined. In Fig. 4b, this sensor system 40a, 40b, 40c is shown schematically as a combined sensor system, which includes a temperature sensor and a flow meter, but these can in principle also be arranged separately from one another. The respective sensor system 40a, 40b, 40c is connected to the mixing cell control device 21a in a signal-conducting manner, which can then use a corresponding algorithm to determine how the respective inlet valves 26a, 26b, 26c, 26d are to be controlled in order to enter the mixing chamber 21b to generate such a mixture of gaseous nitrogen GN from the different nitrogen sources that a nitrogen stream 20 is generated at the outlet 28 with the predetermined throughput NDS or the target temperature TS20 for the respective impact mill 4.

For control purposes, a sensor system 40 (with a temperature sensor and a flow meter) is also arranged on the drain 28, which measures the outgoing gaseous nitrogen flow 20 so that a target / actual comparison can be carried out in the mixing cell control device 21a. In particular, it can be provided that for a suitable tempering of the nitrogen flow 20 by a corresponding control of the fourth inlet valve 26d, such an amount of liquid nitrogen LN is admitted into the mixing chamber 21b that the nitrogen flow temperature measured by the sensor system 40 increases T20 at the outlet 28 approaches the specified nitrogen flow target temperature TS20.

If, for example, the gaseous nitrogen GN flowing in via the first inflow 25a from the precooling gas flow 17 from the first and / or a second countercurrent precooling unit 16a, 16b - after the Pre-cooling of the ground material 3 in countercurrent - be used as the basic source flow, the mixing cell 21 can add or mix in the part from the other inflows 25b, 25c, 25d in the mixing chamber 21b by appropriate automatic control of the inlet valves 26b, 26c, 26d, which is missing in order to obtain a predetermined nitrogen flow target temperature TS20 at a predetermined nitrogen flow target throughput NDS, from which, depending on the impact mill 4, a corresponding grist flow density Rho results, for which an effective brittle fracture during grinding can be ensured.

In order to make the precooling more flexible, a second countercurrent precooling unit 16b can be provided in addition to the first countercurrent precooling unit 16a according to FIG. 3. In principle, this can also be provided instead of the first countercurrent pre-cooling unit 16a. The second countercurrent pre-cooling unit 16b is designed in the form of a vortex screw with a vortex screw interior 16c, into which the ground material 3 metered and supplied via the metering screw 5 is transported. The transported ground material 3 passes from the second countercurrent pre-cooling unit 16b via a vortex screw connection 16d already pre-cooled from above into the first counter-current pre-cooling unit 16a, in which it is further pre-cooled in countercurrent according to the process described above for FIG. 2.

At the same time, the pre-cooling gas stream 17 of gaseous stick material GN from the first countercurrent pre-cooling unit 16a via the vortex screw connection 16d also enters the second countercurrent pre-cooling unit 16b (opposite to the transport direction of the regrind 3) and can thereby the regrind 3 in the vortex screw Cool the interior 16c also in a countercurrent via a second pre-cooling section SVb, whereby an intensive thermal exchange of energy can take place due to the turbulent flow conditions in the vortex screw. For fine-tuning mood, liquid nitrogen LN can at least temporarily also be introduced from the nitrogen tank 35 via the nitrogen inlet 7 into the vortex screw interior 16c, for example to prevent excessive bubbling or evaporation of the liquid nitrogen LN in the tank 6b when the system is started up to prevent the supply of relatively warm grist 3.

In order to make the pre-cooling more flexible, a third counter-current pre-cooling unit 16e can be provided in addition or as an alternative to the first counter-current pre-cooling unit 16a and / or the second counter-current pre-cooling unit 16e, which is also formed by the feed silo 2 itself. According to FIG. 3, gaseous nitrogen GN, in particular cold residual gas R, is fed to the feed silo 2 via a bypass line 23 from the pneumatic filter 14 and the blower 15, at least partially on the underside, preferably via the feed silo opening 2a on the underside, in order to with the superfluous existing gaseous nitrogen GN to achieve a pre-cooling of the ground material 3 in countercurrent also in the feed silo 2. At the top, the gaseous nitrogen GN can be discharged in any way.

According to this embodiment, several pre-cooling units 16 are provided, which together form a pre-cooling section SV from the first, second and third pre-cooling section SVa, SVb, SVc, on which the gaseous nitrogen GN acts in countercurrent on the transported ground material 3, so that it is before immersion can be cooled in the cooling unit 6 in several stages to the intermediate grist temperature TZ3. This means that the entire pre-cooling process can also be supported. The number of countercurrent pre-cooling units 16a, 16b, 16e as well as their arrangement to each other is basically selectable, the arrangement shown in Fig. 3 already enabling very efficient pre-cooling if the individual pre-cooling sections SVa, SVb, SVc are specifically coordinated with one another will. In addition, it can be provided according to FIG. 3, the feed silo 2 as a further pre-cooling unit 16 is switched upstream of a container pre-cooling unit 16f, which can be designed, for example, as a closed and inert refrigerated container or a silo. The container pre-cooling unit 16f has a container interior 16g in which the ground material 3 is located for storage and pre-cooling. In this case, the feed silo 2 is supplied with pre-cooled regrind 3 before the regrind 3 is additionally pre-cooled in a countercurrent to the intermediate regrind temperature TZ3 in one, two or three further countercurrent pre-cooling units 16a, 16b, 16e. The container interior 16g is for example pre-cooled in any way to a temperature of less than -10 ° C, preferably less than -30 ° C, in particular less than -70 ° C.

As in the prior art, the fine material stream 90, consisting of the fine material 9 mixed with gaseous nitrogen GN, is passed after the impact mill 4 into a cyclone 10, in which the fine material 9 is separated off. This fine material 9 is then fed into a sieve device 12 in a possibly warmed-up form, in which it is separated into its different fine material fractions, ie coarse grain 11 G and fine grain 11 F (depending on later use via the appropriate sieve cuts to be selected). The coarse grain 11 G is conveyed back to the metering screw 5 in any manner, for example via a repassing line 24, and is thus fed back into the grinding process. The majority of the fine grain 11 F in this variant can have a very high degree of fineness and can accordingly be further used as finished product 13. The grinding limit can be shifted to low values compared to the prior art due to the already addressed, uniform brittleness. The remaining part of the fines stream 90 in the cyclone 10, which in particular consists of gaseous nitrogen GN and fine material dusts 11 S, is separated into its components in the pneumatic filter 14. Since a separation has already taken place in the cyclone 10, the pneumatic cal filter 14 for the residual separation of fine material dusts 11 S and gaseous nitrogen GN is less stressed and can therefore be dimensioned correspondingly small. The fine material dust 11 S is likewise fed into the sieve device 12 in warmed up form, if necessary, and the gaseous nitrogen GN is fed as residual gas R via a fan 15, in particular into the mixing cell 21.

For the embodiments in FIGS. 2 and 3, it is also provided that the ground material 3 and the fine material 9 are kept inert over the entire conveying route within the grinding device. This advantageously ensures that the entire process is not adversely affected by migration of oxygen and air humidity from the ambient air. This can be achieved by appropriately closed system parts in which there is gaseous nitrogen GN and / or overpressure.

In addition, it can be provided that when the Mahlvor device 1b is switched off via the mixing cell 21 by opening the third inlet valve 26c, gaseous nitrogen GN, which is provided by the nitrogen gas generator 22, is fed into the circuit. This can prevent humid ambient air from entering the circuit.

List of reference symbols

1a grinding device (state of the art)

1b grinding device

2 feed silo 2a feed silo opening

3 grist

4 impact mill

4a disintegrator

4b connection

4c fine material output

5 dosing screw

6 cooling unit

6a vortex screw cooler

6b tank

6c top of tank 6b

6d access

7 nitrogen inlet

8 Outlet of the vortex screw cooler 6a

9 fine material

10 cyclone

11 G coarse grain 11 F fine grain 11 S fine material dust 12 sieve device

13 finished goods

14 pneumatic filter

15 fans

16 pre-cooling unit 16a first countercurrent pre-cooling unit 16b second counter-current pre-cooling unit 16c vortex screw interior 16d vortex screw connection 16e third countercurrent pre-cooling unit 16f container pre-cooling unit 16g container interior 17 Pre-Cooling Gas Flow

18 Level limit

19 screw conveyor

20 nitrogen flow 21 mixing cell 21a mixing cell control device 21b mixing chamber 21c heat exchange section 22 nitrogen gas generator

23 Bypass line

24 Repassierleitung

25a, 25b, 25c, 25d inflows into the mixing cell 21

26a, 26b, 26c, 26d inlet valves (throttle valve)

28 drain

30 grist flow

35 nitrogen tank

40 Sensors on the drain

40a, 40b, 40c sensors at the inflow

90 stream of fines

GN gaseous nitrogen

LN liquid nitrogen

MFa, MFb, MFc Actual mass flow in the respective inflow

ND nitrogen flow rate

NDS nitrogen flow target throughput

Rho grist flow density

SV pre-cooling section

SVa first pre-cooling section

SVb second pre-cooling section

SVc third pre-cooling section

T20 nitrogen flow temperature

TS20 nitrogen flow target temperature TA3 regrind starting temperature

TA9 fine material outlet temperature

TE3 regrind inlet temperature

Tla, Tlb, Tic Actual temperature in the respective inflow TLN nitrogen liquid temperature TZ3 intermediate grist temperature TZN intermediate nitrogen temperature

Claims

1. Grinding device (1 b) for grinding ground material (3), in particular made of thermoplastics and / or elastomers, with

- A cooling unit (6) with liquid nitrogen (LN) for cooling supplied regrind (3) to a regrind starting temperature (TA3) and

- An impact mill (4) connected downstream of the cooling unit (6) for grinding the ground material (3) cooled to the ground material starting temperature (TA3) into fine material (9), the impact mill (4)

- At least one connection (4b) for supplying the millbase (3) cooled to the millbase output temperature (TA3) and a stick material flow (20) of gaseous nitrogen (GN) in the impact mill (4) and

- Has a fine material outlet (4c) for discharging the fine material (9) produced in the impact mill (4), characterized in that at least one pre-cooling unit (16) is also provided, with the ground material (3) provided by the at least one pre-cooling unit (16) can be pre-cooled to an intermediate regrind temperature (TZ3), the at least one pre-cooling unit (16) being connected upstream of the cooling unit (6) in such a way that the at least one pre-cooling unit (16) affects the intermediate regrind -Temperature (TZ3) pre-cooled grist (3) after being fed into the cooling unit (6) in the liquid nitrogen (LN), a mixing cell (21) is also provided, the mixing cell (21) being designed to Nitrogen flow (20) made of gaseous nitrogen (GN) with a predetermined nitrogen flow target temperature (TS20) and a predetermined nitrogen flow target throughput (NDS) to be provided and fed to the connection (4b) of the impact mill (4) n, for the reproducible achievement of a high degree of fineness of the discharged Fine goods (9).

2. Grinding device (1b) according to claim 1, characterized in that the mixing cell (21) has a plurality of inflows (25a, 25b, 25c, 25d) and an outflow (28), the mixing cell (21) via the plurality of inflows ( 25a, 25b, 25c, 25d) for example

- Gaseous nitrogen (GN) from a nitrogen gas generator (22) and / or residual gas (R) from a pneumatic filter (14) and / or a pre-cooling gas flow (17) from the at least one pre-cooling unit (16) and / or

- Liquid nitrogen (LN) can be supplied from a nitrogen tank (35).

3. Grinding device (1b) according to claim 2, characterized in that the mixing cell (21) further comprises a mixing chamber (21b), wherein the gaseous nitrogen (GN) and the Liquid nitrogen (LN) evaporating in the mixing chamber (21b) can be mixed in the mixing chamber (21b) on a heat exchange path (21c) in such a way that the outflow (28) connected to the connection (4b) of the impact mill ( 4) is connected, a nitrogen flow (20) with the predetermined nitrogen flow target temperature (TS20) and the predetermined nitrogen flow target throughput (NDS) forms.

4. grinding device (1b) according to claim 3, characterized in that at least some inflows (25a, 25b, 25c, 25d) an inlet valve (26a, 26b, 26c, 26d), in particular a finely adjustable throttle valve, is assigned, wherein the respective inlet valve (26a, 26b, 26c, 26d) is formed from a supply of gaseous nitrogen (GN) and / or liquid nitrogen (LN) via the respective inlet (25a, 25b, 25c, 25d) into the mixing chamber (21 b) to dose.

5. Grinding device (1b) according to claim 3 or 4, characterized in that at least each inflow (25a, 25b, 25c) through the gaseous nitrogen (GN) can be passed into the mixing chamber (21b), a sensor system (40a, 40b, 40c), the sensor system (40a, 40b, 40c) being designed to provide an actual mass flow (MFa, MFb. MFc) and / or an actual temperature (Tla, Tlb, Tic) of the gaseous nitrogen (GN ) to be recorded in the respective inflow (25a, 25b, 25c)

6. Grinding device (1b) according to one of claims 3 to 5, characterized in that the outflow (28) is assigned a sensor system (40) which is designed to provide a nitrogen flow temperature (T20) and / or a nitrogen flow throughput ( ND) to measure the nitrogen flow (20) discharged from the drain (28).

7. Grinding device (1b) according to one of claims 3 to 6, characterized in that the mixing chamber (21b) has a heat exchange path (21c) which is meandering in section.

8. Grinding device (1b) according to one of claims 3 to 7, characterized in that the mixing cell (21) has a mixing cell control device (21a), the mixing cell control device (21a) being designed, the inlet valve (26a, 26b, 26c, 26d) of the respective inflow (25a, 25b, 25c, 25d) in such a way that the mixing chamber (21b) is supplied with gaseous nitrogen (GN) and / or liquid nitrogen (LN) and gaseous nitrogen (GN) is in the mixing chamber (21b) is mixed in such a way that a nitrogen flow (20) with the specified nitrogen flow target temperature (TS20) and the specified nitrogen flow target throughput (NDS) is formed at the outlet (28) of the mixing cell (21) .

9. Grinding device (1 b) according to one of the preceding claims, characterized in that the grist (3) cooled to the grist starting temperature (TA3) and the nitrogen stream (20) provided by the mixing cell (21) of gaseous nitrogen ( GN) independently dosed and individually tempered provided before they are fed to the impact mill (4) via the at least one connection (4b) in order to reproducibly achieve a high degree of fineness of the discharged fine material (9).

10. Grinding device (1b) according to one of the preceding claims, characterized in that as a pre-cooling unit (16) at least one countercurrent pre-cooling unit (16a, 16b, 16e) each with a pre-cooling section (SVa, SVb, SVc) and / or at least one Container pre-cooling unit (16f) with a container interior (16g) is provided, the at least one countercurrent pre-cooling unit (16a, 16b, 16e) being designed, in which at least one countercurrent pre-cooling unit (16a, 16b, 16e) there is ground material (3) to precool in a countercurrent of gaseous nitrogen (GN) within the respective pre-cooling section (SVa, SVb, SVc), and the container pre-cooling unit (16f), for example a refrigerated container, is designed in the container interior (16g) to pre-cool the grist (3).

11. Grinding device (1b) according to claim 10, characterized in that the at least one countercurrent pre-cooling unit (16a, 16b) is connected directly or indirectly upstream of the cooling unit (6) in such a way that one in the cooling unit (6) by evaporation of the liquid Nitrogen (LN) formed pre-cooling gas flow (17) into which at least one countercurrent pre-cooling unit (16a, 16b) can be introduced in order to remove the ground material (3) located in the respective counter-current pre-cooling unit (16a, 16b) within the respective pre-cooling section (SVa, SVb) in one To precool countercurrent through the precooling gas flow (17) to an intermediate millbase temperature (TZ3).

12. Grinding device (1b) according to claim 10 or 11, characterized in that a first countercurrent pre-cooling unit (16a) forms in such a way and the cooling unit (6) is connected directly or indirectly in front of the first countercurrent pre-cooling unit (16a ) fed ground material (3) can fall due to gravity along a first pre-cooling section (SVa) of the first countercurrent pre-cooling unit (16a) and the fed, falling ground material (3) at the same time in a countercurrent of gaseous nitrogen (GN), preferably the pre-cool -Gas stream (17), can be pre-cooled within the first pre-cooling section (SVa).

13. Grinding device (1b) according to one of claims 10 to 12, characterized in that a second countercurrent pre-cooling unit (16b) is designed in such a way and directly or indirectly upstream of the cooling unit (6) that the second countercurrent pre-cooling unit (16b ) supplied grinding stock (3) can be transported in a vortex screw interior (16c) along a second pre-cooling section (SVb) and the supplied grinding stock (3) at the same time in a countercurrent of gaseous nitrogen (GN), preferably the pre-cooling gas flow (17 ), can be pre-cooled within the second pre-cooling section (SVb) while mixing with the gaseous nitrogen (GN).

14. Grinding device (1b) according to claim 13, characterized in that liquid nitrogen (LN) can be fed to the vortex screw interior (16c) via a nitrogen inlet (7), for example from a nitrogen tank (35).

15. Grinding device (1b) according to one of claims 10 to 14, characterized in that a third countercurrent pre-cooling unit (16e) is formed by a feed silo (2), the feed silo (2) providing grist (3) for the grinding process, wherein gaseous nitrogen (GN), for example residual gas (R) from a pneumatic filter (14), can be introduced into the feed silo (2) in such a way that the ground material (3) located therein is countercurrent within a third pre-cooling section (SVc) can be pre-cooled before the ground material (3) is discharged from the feed silo (2).

16. Grinding device (1b) according to one of the preceding claims, characterized in that the impact mill (4) is a high-speed impact mill, for example a pin mill, a vortex mill, an air vortex mill, a disintegrator (4a), etc. for grinding the cooled material to be ground (3) to fine material (9) due to impact-impact stress.

17. Grinding device (1b) according to one of the preceding claims, characterized in that the at least one pre-cooling unit (16), in particular the at least one countercurrent pre-cooling unit (16a, 16b), is preceded by a metering screw (5), the metering screw ( 5) the grist (3) provided by the feed silo (2) and / or from a Siebvor device (12) in a metered manner into the at least one countercurrent pre-cooling unit (16a, 16b).

18. Grinding device (1b) according to one of the preceding claims, characterized in that the cooling unit (6) is followed by a screw conveyor (19), preferably a motor-driven screw conveyor (19), the screw conveyor (19) being the on the ground material -Outlet temperature (TA3) cooled ground material (3) dosed to at least one connection (4b) of the impact mill (4), the ground material (3) cooled to the ground material output temperature (TA3) pre- preferably on the underside of the cooling unit (6) can be removed.

19. Grinding device (1b) according to one of the preceding claims, characterized in that the ground material (3) and / or the fine material (9) are kept inert within the entire grinding device (1b).

20. A method for grinding millbase (3), preferably made of thermoplastics and / or elastomers, in particular with a grinding device (1b) according to one of the preceding claims, with at least the following steps:

- Provision of regrind (3) and supply of the regrind (3) in min least one pre-cooling unit (16) for pre-cooling the supplied regrind (3) to an intermediate regrind temperature (TZ3);

- Feeding of the regrind (3), which has been pre-cooled to the intermediate regrind temperature (TZ3), into a cooling unit (6) with liquid nitrogen (LN), so that the pre-cooled regrind (3) is transferred to a regrind by the liquid nitrogen (LN) Output temperature (TA3) is cooled;

- Conveying the ground material (3) cooled to the ground material starting temperature (TA3) into an impact mill (4);

- Milling of the millbase (3) cooled down to the millbase output temperature (TA3) to give fines (9) with simultaneous supply of a nitrogen stream (20) made of gaseous nitrogen (GN), the nitrogen flow (20) made of gaseous nitrogen ( GN) of the impact mill (4) with a predetermined nitrogen flow target temperature (TS20) and a predetermined nitrogen flow target throughput (NDS) is made available in order to give the impact mill (4) a defined grist flow density (Rho) Grist stream (30) from the grist (3) and the nitrogen stream (20) to provide for reproducible achievement of a high degree of fineness of the discharged fine material (9).

21. The method according to claim 20, characterized in that the cooled ground material (3) and the nitrogen stream (20) made of gaseous stick material (GN) are dosed independently of one another and individually tempered are provided before they are fed to the impact mill (4) .

22. The method according to claim 20 or 21, characterized in that the nitrogen flow target temperature (TS20) and the nitrogen flow target throughput (NDS) of the nitrogen flow (20) fed to the impact mill (4) as a function of the impact mill (4 ) and / or is specified as a function of the ground material (3) given.