EP3292912B1 - Method for operating a multicyclone for separating fine and micro grain and multicyclone - Google Patents

Description

The invention relates to a method for operating a multicyclone for separating fine and very fine grain, and a multicyclone.

Generic methods with a plurality of individual cyclones of essentially the same structure, each having a carrier gas inlet opening, a carrier gas outlet opening and a semolina discharge opening, are known. In this case, the individual cyclones are housed together in a housing with little air intake, in which an upper and a lower chamber is formed. The carrier gas outlet openings of the individual cyclones are designed to be open towards the upper chamber and the upper chamber has an overall carrier gas outlet opening. This serves to discharge the carrier gas, which has in each case emerged from the respective carrier gas outlet openings of the individual cyclones into the upper chamber, via the entire carrier gas outlet opening from the housing of the multicyclone. The semolina discharge openings of the individual cyclones are each designed to be open towards the lower chamber. In addition, the lower chamber has a device for extracting cyclone grits introduced through the semolina outlet openings with little air intake. A common cyclone control air supply is also provided to the lower chamber.

Single cyclones are also called centrifugal separators. They serve, for example, as so-called mass force separators in process engineering systems for separating solid particles from gases. For example, they are used for exhaust gas purification. The aim here is to use the cyclone to clean the carrier gas, which transports the particles into the cyclone, as completely as possible, that is to say to a very high degree of purity, and again from the cyclone dissipate. Ideally, a degree of cleaning of over 99% is achieved depending on the particle size and mass.

Essential components of a centrifugal separator are an upper inlet cylinder, a conical extension of this cylinder and an immersion tube. A cyclone works as follows. Carrier gas with the particles to be separated is blown tangentially into the inlet cylinder so that it describes a circular path. The particles in the carrier gas are guided by their centrifugal force to the wall of the cylindrical region and braked in the subsequent conical region, in particular to the cone walls, so that they fall out of the carrier gas stream and leave the cyclone at the bottom. The carrier gas thus cleaned exits the cyclone via the immersion tube which extends inside the inlet cylinder and the subsequent cone.

From the PCT / EP2015 / 066348 it is known that a cyclone can also be used to separate or classify fine particles. It is taught here that the separation properties of the cyclone can be influenced in part by the rate of inflow of the carrier gas stream into a cyclone. However, since the carrier gas flow or process gas flow can often not be influenced arbitrarily in process engineering plants due to further apparatuses installed in such plants, such a regulation has proven to be not always optimally feasible.

From the FR 1 517 649 A A device is known which has a plurality of multicyclones, the individual multicyclones being provided in a common housing, as a result of which an upper and lower chamber is formed. Carrier gas can escape into the upper chamber. In addition, the lower chamber has a common semolina discharge opening.

The invention is therefore based on the object of providing a simple and efficient method for operating a multicyclone for separating fine and very fine particles and a multicyclone.

This object is achieved according to the invention by a method for operating a multicyclone for separating fine and very fine grain with the features of claim 1 and by a multicyclone with the features of claim 8.

Advantageous embodiments of the invention are specified in the subclaims and the description as well as their figures and their explanations.

In the method according to the invention it is provided that the carrier gas inlet openings each have a carrier gas stream of equal volume from outside the housing with the fine and very fine grain to be separated as particles. In the individual cyclones of the multicyclone, an at least partial separation of fine and very fine grain is carried out, the fine grain entering the lower chamber as cyclone semolina via the semolina discharge openings and from there being withdrawn from the housing via the device for low-air intake. The finest grain is fed out of the multicyclone as a cyclone fine material by means of the carrier gas flow via the upper chamber and the carrier gas outlet opening. Furthermore, it is provided that the amount, the fineness and / or the purity of the fine grain discharged from the multicyclone is adjusted by regulating the amount of the cyclone control air fed into the lower chamber through the cyclone control air supply.

False air entry arm or poorly air or poorly airless in the sense of the invention can be understood such that hardly or ideally no air or gas can penetrate into the multicyclone from outside the multicyclone. However, it is not possible to completely prevent the ingress of false air or incorrect air in real circumstances, or it can only be achieved with unreasonable effort. The main reason for the entry of incorrect air into the multi-cyclone is the device for extracting cyclone sizes discharged through the semolina discharge openings with little air intake. Such a device can be implemented, for example, as a rotary valve. Cell wheel locks that meet the requirements of the invention described here have, for example, a gap width of approximately 0.3 mm. Overall, it is possible to state that the entry of false air in the sense of the invention ideally approaches zero as far as possible, but in real scenarios should be a maximum of 1%.

The term “carrier gas flow” is used in the context of the present description. For the purposes of the invention, this can be a gas or air flow with which the particles to be separated, which are referred to as fine and very fine particles, are transported. In principle, any gas or gas mixture can be used for this. For example, it can be ambient air, oxygen-depleted process gas or the like.

A basic idea of the invention can be seen in supplying the individual cyclones provided in the multicyclone with a carrier gas stream of equal volume. The result of this is that the individual cyclones have essentially the same separation characteristics between fine and ultra-fine grains, which significantly simplifies regulation of this separation limit across the entire multicyclone.

Furthermore, it was recognized in accordance with the invention that, in the sense of a simple structure and simple regulation of the multicyclone, it is preferable to use cyclone control air as the control variable for the separation limit, that is to say in particular for the quantity, the fineness and / or purity of the fine grain becomes. A simple regulation is also provided by the fact that the cyclone control air is not supplied separately to each individual cyclone, but rather a common single supply of the cyclone control air to the lower chamber of the multicyclone is provided. Of course, several feeds into the lower chamber could also be provided due to the design. It is essential here, however, that the supply and thus also the regulation of the cyclone control air take place in the lower chamber and not in each individual cyclone itself and directly.

It is central to the invention that it was recognized that by supplying cyclone control air, the vortex or vertebral sink that forms within the cyclone is disturbed, so that 99% or even better separation of the solid particles in the carrier gas stream is no longer possible. Coarser, that is to say particles with a higher density, then tend to be separated, whereas smaller or finer particles with a lower density can no longer be separated from the carrier gas stream and are carried away via the carrier gas stream emerging from the cyclone.

It is advantageous if the volume per unit time of the carrier gas streams of the same volume to the individual cyclones is set depending on the geometry of the individual cyclones used, in order to separate approximately 99% of the fine and very fine grain in the carrier gas streams as cyclone semolina when the cyclone control air supply is closed. It has been found that a basic state set in this way can be regulated or controlled particularly efficiently and effectively by supplying cyclone control air. This results from the fact that the single cyclones of the multicyclone are operated in this basic state in such a way that they enable the most complete separation of the fine and fine particles. Subsequently, this separation can be worsened by the supply of cyclone control air, so that the goal is achieved to remove part of the particle in the carrier gas stream as a fine particle from the multicyclone by means of the carrier gas total outlet stream and to feed it to a later separation.

As an alternative or in addition to setting the volume per unit of time of the carrier gas flows of the same volume to the individual cyclones, the loading of the carrier gas flows of the same volume to the individual cyclones with fine and very fine grain can also be adjusted depending on the geometry of the individual cyclones, in order to achieve approximately 99% of the total when the cyclone control air supply is closed to separate fine and ultra-fine grains from the carrier gas flows as cyclone semolina. In a similar way to the volume per unit time of the carrier gas streams of the same volume, the loading of the carrier gas streams of the same volume with particles which can be separated as fine and very fine particles is a relevant variable for setting a stable basic state. The load can be specified as grams of dust particles per cubic meter of carrier gas or as kilograms of dust particles per kilogram of carrier gas.

It is preferable to set a load that fulfills the conditions specified above, since if the load is too high, 99% separation of fine and very fine particles as cyclone semolina is fundamentally not possible, and regulation via cyclone control air is thus made more difficult. Of course, the loading should be optimized as desired, since it has a significant influence on the effectiveness of the multicyclone. This means that the closer the load is to the optimum, that is to say with a 99% separation without the supply of cyclone control air, the greater the throughput can be achieved with such a multicyclone.

It is preferred if a pressure difference between the upper and the lower chamber is set during operation and the pressure in the upper chamber is lower than the pressure in the lower chamber. This can be achieved, for example, by means of a suction fan after the multicyclone, so that a pressure drop arises in the entire multicyclone. As a result, the static pressure in the upper chamber is lower than in the lower chamber. It is therefore easy to achieve that the cyclone control air introduced into the lower chamber flows through the individual cyclones into the upper chamber, and thus has the desired effect on the separation properties of the individual cyclones.

In this regard, it is advantageous if the pressure in the upper chamber and in the lower chamber is set lower than the ambient pressure. This ensures that the cyclone control air does not have to be blown into the multicyclone itself, but is sucked into it. Such a method simplifies the construction and operation of a multicyclone, since it is necessary for the process to either blow the carrier gas streams actively into the multicyclone or, as is preferred, to suck through the multicyclone via a blower.

In principle, the fine and very fine particles to be separated can be fed directly into a carrier gas stream. However, it is advantageous if the fine and ultra-fine grain to be separated is fed into the multicyclone by means of the carrier gas of a dispersing unit prior to the task, and is transported from there to the multicyclone by means of the carrier gas stream. Such a method is particularly advantageous when the fine and ultra-fine grain is not supplied directly from an upstream process via the carrier gas stream, but from a storage location such as a bunker. The use of a dispersion unit ensures that the fine and ultra-fine particles are distributed as homogeneously as possible in the carrier gas stream and that hardly any particles adhere to one another. This has a positive effect on the result of the separation in the multicyclone.

In principle, the fine grain which is discharged from the multicyclone by means of the carrier gas outlet stream can be separated from the carrier gas stream in any manner. It is advantageous if this is carried out using a filter. For example, a bag filter or cartridge filter can be used as the filter.

The method according to the invention can advantageously be applied to a multicyclone with a plurality of individual cyclones of essentially the same structure. These individual cyclones each have a carrier gas inlet opening, a carrier gas outlet opening and a semolina discharge opening. The individual cyclones are housed together in a housing with little air intake, in which an upper and a lower chamber is formed. The carrier gas outlet openings of the individual cyclones are designed to be open towards the upper chamber. This upper chamber has a total carrier gas outlet opening in order to discharge the carrier gas which enters the upper chamber from the respective carrier gas outlet openings of the individual cyclones via this total carrier gas outlet opening from the housing of the multicyclone. The semolina discharge openings of the individual cyclones are each designed to be open toward the lower chamber, the lower chamber having a device for the removal of cyclone grits introduced through the semolina discharge opening with little air intake.

The carrier gas inlet openings are designed in such a way that they can each be acted upon with a carrier gas flow of the same volume from outside the housing of the multicyclone and are not connected in terms of flow technology to the upper or the lower chamber. A common cyclone control air supply is provided to the lower chamber, via which cyclone control air can be directed into the lower chamber. In addition, a control and regulating device is provided and set up in order to set the amount, the fineness and / or the purity of the fine grain guided from the multicyclone by means of the amount of cyclone control air per unit time.

With such a construction according to the invention, it is relatively easy to adjust the amount, fineness and / or purity of the fine grain separated by means of the multicyclone by adjusting the cyclone control air volume per unit time.

The entire structure of the multicyclone is such that there is a common cyclone control air supply to all individual cyclones. This means that only one feed, which leads centrally into the lower chamber, has to be adjusted and / or regulated in order to influence the properties of the fine grain mentioned above.

To make this easy, the individual cyclones are fluidically connected to the lower chamber via their semolina discharge openings. The supply of cyclone control air via the lower chamber and the semolina discharge openings into the individual cyclones influences the vertebral sink, which is formed in each of the individual cyclones and is largely responsible for the selectivity or other separation properties in a cyclone. The more this spine sink is influenced, the more the separation limit shifts from the area of fine grain to the area of fine grain.

An advantage of such an embodiment is that the carrier gas stream which is fed to the individual cyclones does not have to be modified or influenced here. This means that the multicyclone during operation is once set to an ideally optimal operating point and then the separation properties only have to be varied and readjusted via the amount of cyclone control air supplied per unit of time.

The construction of the multicyclone according to the invention thus has the advantage that the multicyclone can in principle be set at an optimal operating point with regard to the amount of carrier gas flowing in and its loading and can thus be operated in an efficient manner.

In principle, the individual cyclones can be arranged arbitrarily in the multi-cyclone. With regard to simple control of the multicyclone, it is preferred if the individual cyclones are provided in the housing in terms of flow technology in parallel. This means that they all have a respective individual carrier gas inlet opening which is supplied with carrier gas laden with particles from outside the multicyclone.

The parallel arrangement ensures that the individual cyclones, which are essentially of identical design, each behave identically and thus have a similar separation behavior. There is also the advantage that the multicyclone can be easily scaled by providing additional individual cyclones in parallel, since these only have to be provided in the common housing. This again shows the advantage of the common cyclone control air supply, so that no additional new cyclone control air supply is necessary for a further individual cyclone.

It is preferred if the upper and the lower chamber are made airtight with respect to one another, an air exchange between the upper and the lower chamber taking place essentially only via the individual cyclones. Airtight in this sense means that an air exchange between the two chambers can take place exclusively via or through the individual cyclones, so that no direct air exchange is provided between these two chambers. The airtight separation of the Upper and lower chamber has the result that the cyclone control air can only flow into the single cyclones via the semolina outlet openings of the individual cyclones and into the upper chamber via the carrier gas outlet openings. With such a construction it is achieved that the cyclone control air introduced into the lower chamber flows completely through the individual cyclones and is thus fully used to control the separation between fine and very fine particles.

A multicyclone according to the invention can preferably be used or installed in the context of a fine grain separator for separating fine and fine grain from a preliminary or intermediate product. In addition to a multicyclone according to the invention, such a fine grain separator has a filter connected downstream of or downstream of the multicyclone. The preliminary or intermediate product is fed to at least one multicyclone by means of a carrier gas stream. In the multicyclone, the fine grain can be separated as cyclone semolina. The fine grain, which is still in the carrier gas stream, is then passed on to the filter, where it can be separated. Such a fine grain separator makes it possible in a simple manner to further treat the carrier gas stream emerging from the multicyclone, in which the fine grain not separated out in the cyclones is present, so that the fine grain can also be obtained from the carrier gas stream, and the carrier gas stream itself either Process can be fed again or can be directed into the environment.

Furthermore, it is possible to provide several multicyclones in series in flow terms in front of the filter. The respective individual cyclones of the plurality of multicyclones are each equipped with a smaller diameter in the flow direction of the carrier gas stream. In other words, a plurality of multicyclones can be arranged in a cascading manner in front of the filter, the diameter of the individual cyclones becoming smaller the closer the multicyclone is arranged to the filter in the flow direction.

The diameter of a single cyclone is largely responsible for the options for setting the separation limit. The smaller the diameter, the further the separation limit between fine and very fine grain can be shifted in the direction of the fine grain or smaller diameter, so that the fine grain is finer. It is with such a cascading arrangement of several multicyclones It is therefore possible to produce different fractions of fine or very fine grain with a fine grain separator.

In principle, the preliminary or intermediate product can be fed to the fine grain separator directly from a process-technical plant, for example a grinding process. In this case, however, since the volumes of the carrier gas flows are often defined based on the upstream process, it is not easy to operate the multicyclone at an efficient operating point.

It is therefore advantageous if a storage bunker for the preliminary and intermediate product and a dispersion unit are provided in front of the multi-cyclone (s) of the fine grain separator. The preliminary or intermediate product to be separated is fed from the storage bunker via the dispersing unit to the fine grain separator by means of the carrier gas stream. With such a structure, the fine grain separator can be decoupled from an upstream process and can thus be operated independently of its operating state. The use of a dispersing unit after the storage bunker has proven to be advantageous, since the dispersing unit ensures that the fine and very fine particles to be conveyed further by means of the carrier gas stream are present homogeneously and essentially without adhesions in the carrier gas stream, so that a good separation in the Multicyclone is enabled.

The fine grain separator can also be used in a grinding plant to produce fine and fine grain from a raw material. Such a grinding plant has a mill-sifter combination, which has a sifter and a mill. Here, the mill-sifter combination is designed to feed raw material from the sifter to the mill-sifter combination, which has been crushed at least once, as rejected coarse material of the mill for further comminution.

A grinding plant filter is also provided. By means of a grinding plant carrier gas stream, crushed ground material which has not been rejected is transported from the classifier of the mill-classifier combination to the grinding plant filter and is separated there from the grinding plant carrier gas flow. Then, directly or indirectly, for example via a bunker, the crushed ground material separated on the grinding plant filter is fed to the fine grain separator, where it is separated into fine and fine grain.

In principle, any type of mill construction can be used which enables the ground material to be reduced to the desired fineness. It has proven to be advantageous to use a vertical mill with a grinding plate and grinding rollers for this purpose, since this achieves a good comminution result and a large range of grain fractions occurs during the comminution, so that fine and very fine particles of both fractions are present in the carrier gas stream. It is also advantageous that a vertical mill can be operated relatively energy-efficiently in this process compared to ball mills.

Fig. 1

eine skizzenhafte Darstellung eines erfindungsgemäßen Multizyklons;

Fig. 2

ein schematisches Flussdiagramm eines erfindungsgemäßen Feinstkornabscheiders mit Dispergiereinheit und Vorratsbunker;

Fig. 3

ein schematisches Flussdiagramm einer Mahlanlage mit erfindungsgemäßen Feinstkornabscheider, und

Fig. 4

ein kombiniertes schematisches Diagramm zur Erläuterung der Zyklonregelluftmenge und der Staubbeladung des Trägergases in Bezug auf die Feinheit.

The invention is explained below using examples with the aid of schematic figures. Here show:

Fig. 1

a sketchy representation of a multicyclone according to the invention;

Fig. 2

is a schematic flow diagram of a fine grain separator according to the invention with a dispersing unit and storage bunker;

Fig. 3

a schematic flow diagram of a grinding plant with fine grain separator according to the invention, and

Fig. 4

a combined schematic diagram to explain the cyclone control air volume and the dust loading of the carrier gas in relation to the fineness.

In Fig. 1 a schematic representation of a multicyclone 1 according to the invention is shown. In the multi-cyclone 1, a plurality of individual cyclones 10 of identical construction are arranged in a housing 3, six in the exemplary embodiment shown here six times six, ie 36. In Fig. 1 only six individual cyclones 10 are visible. The further individual cyclones 10 are located in the depth direction of the sketch. The individual cyclones 10 are preferably used in a square arrangement.

The individual cyclones 10 are essentially identical in design and each have a carrier gas inlet opening 11, a carrier gas outlet opening 12 and one Semolina discharge opening 13. The housing 3 is divided into an upper chamber 5 and a lower chamber 6 by means of a separation 15.

The individual cyclones 10 are each arranged between the upper chamber 5 and the lower chamber 6. The carrier gas inlet openings 11 of the individual cyclones 10 are designed such that they can be operated with a carrier gas stream from outside the housing 3. The carrier gas is fed into the carrier gas inlet openings 11 of the individual cyclones 10 directly from outside the housing 3, so that the carrier gas does not first penetrate into the upper chamber 5 or lower chamber 6.

Each individual cyclone 10 is fluidically connected to the upper chamber 5 via its carrier gas outlet opening 12. In an analogous manner, each individual cyclone 10 is fluidically connected to the lower chamber 6 via its semolina discharge opening 13. The upper chamber 5 has a total carrier gas outlet opening 7, via which carrier gas, which enters the upper chamber 5 from the carrier gas outlet openings 12 of the individual cyclones 10, can emerge from the latter.

On the lower chamber 6, a device is provided for the extraction of cyclone semolina with little or no air. This device can be designed, for example, as a cellular wheel sluice 8, so that the cyclone grits can be removed from the lower chamber 6 without large amounts of air being able to enter the lower chamber 6.

In addition, a cyclone control air supply 9 is provided in the lower chamber 6. Via this cyclone control air supply 9, air or gas can be directed into the lower chamber 6 in a targeted manner. For this purpose, a volume flow measurement 62 and a control flap 61 are arranged in front of the cyclone control air supply 9, with which the volume or the amount of the cyclone control air introduced into the lower chamber 6 can be varied and adjusted.

The operation and the mode of operation of the multicyclone 1 according to the invention will now be explained in more detail below.

According to the invention, the multicyclone 1 is not used for cleaning an air or gas flow of particles, as is conventionally customary, but rather as a targeted separation unit of particles that are present within a carrier gas stream. For this purpose, a carrier gas flow is conducted into the individual individual cyclones 10, which are each arranged in parallel in terms of flow technology, that is to say next to and behind one another, with a corresponding particle loading.

In the context of the invention, reference is made in this regard to fine and very fine grain, a separation between fine and fine grain to be carried out. The carrier gas loaded with particles is distributed to the individual individual cyclones 10 with the same volume per unit of time and the same loading of particles, so that the individual cyclones 10 have the same possible separation characteristics or separation properties. Due to the geometry of the inlet cylinder and the cone of the individual cyclones 10, it is possible in a known manner to separate the particles from the carrier gas stream. The separated particles are transferred via the semolina discharge opening 13 into the lower chamber 6 as cyclone semolina or fall into the latter. The carrier gas, which has essentially been cleaned of the particles, can then enter the upper chamber 5 from the individual cyclones 10 via the carrier gas outlet opening 12 and in turn leave the upper chamber 5 via the entire carrier gas outlet opening 7.

The separation of the particles in the individual cyclone 10 essentially takes place in that the geometry of the cyclone accelerates the carrier gas located on a circular path with the particles, so that the particles emerge from and after the accelerated carrier gas flow due to centrifugal force and gravity fall out below through the semolina discharge opening 13. The carrier gas cleaned in this way can then emerge from the individual cyclone 10 via a dip tube provided, as already described, and via the carrier gas outlet opening 12.

The flow conditions occurring within a single cyclone 10 are also referred to as a vertebral sink. If this vertebral sink is disturbed, for example by cyclone control air which flows into the single cyclone 10 via the semolina discharge openings 13, the flow rate of the carrier gas in the single cyclone 10 changes, so that even lighter particles, which are referred to here as very fine particles, via the dip tube from the single cyclone 10 can emerge and are not separated out as semolina via the semolina discharge opening 13.

The invention makes use of this knowledge by specifically supplying cyclone control air via the cyclone control air supply 9 into the lower chamber 6 of the multicyclone 1. It is important here that it is ensured that the supplied cyclone control air flows through the individual cyclones 10 and influences the vertebra. This can be done, for example, by providing a suction blower downstream of the total carrier gas outlet opening 7, which sucks the carrier gas through the multicyclone 1. In this way, the static pressure in the upper chamber 5 is lower than in the lower chamber 6, the pressure there again being lower than the ambient pressure. In this way, the cyclone control air can be supplied by means of the control flap 62 by opening and closing the lower chamber 6.

In order to achieve effective operation of the multicyclone 1 according to the invention, it has been found that it is advantageous to adjust the amount of the carrier gas and its loading with particles in such a way that 99% or even better separation of the particles in the individual cyclones 10 when the cyclone is closed Cyclone control air supply 9 is reached. If cyclone control air is now supplied in a targeted manner, the separation rate can be changed so that some of the particles can be removed as fine particles via the total carrier gas stream emerging from the multicyclone 1 and can be separated therefrom later.

In other words, the cyclone control air can be used to set the mass flow distribution between the very fine material which is discharged from the multicyclone and the fine material which is separated out as cyclone semolina in the multicyclone. This means that when the cyclone control air supply 9 is completely open, approximately 100% of the particles present in the carrier gas stream are discharged out of the multicyclone 1 again via the total carrier gas outlet opening 7. In contrast, approximately 100%, more precisely by approximately 99%, of the particles in the carrier gas stream with completely closed cyclone control air supply 9 are separated out as cyclone semolina in the multicyclone 1.

For example, it is possible to separate particles with 5000 Blaine, ie .ca D50 = 8 µm, and use single cyclones with a diameter of 150 mm fine grain with a fineness of D50 <6 µm with a correspondingly set cyclone air volume. Basically can it should be noted that the area of optimal separation is essentially also defined by the geometry, in particular the diameter of the individual cyclones. This can also be called selectivity of a single cyclone. In connection with the cyclone control air, the fineness of the fine material can be defined and readjusted in a certain band area.

The D50 value describes the particle size distribution for a particle size distribution in which 50% by mass is larger and 50% by mass is smaller than the specified diameter of the boundary particle. In particular with the subtleties here, it has been found that this size is more suitable than the usual Blaine specific surface.

In Fig. 2 The multicyclone 1 according to the invention is shown in the context of a fine grain separator 40. The fine grain separator 40 has as essential elements a storage bin 42 for a preliminary or intermediate product to be separated. Furthermore, a dispersing unit 20 is provided in order to be able to distribute the preliminary or intermediate product to be separated as homogeneously as possible in a carrier air stream. A multicyclone 1 according to the invention is then used, to which a filter 30, which is preferably designed as a bag filter, is connected downstream.

The structure of the finest grain separator 40 will now be discussed in more detail below, with its function and operating mode also being described at the same time.

The preliminary or intermediate product stored in the bunker 42 is fed via a cellular wheel sluice 43 to a speed-controlled conveyor screw 44, which feeds the preliminary or intermediate product to the dispersion unit 20. In principle, removal from the bunker and feeding to the dispersing unit 20 can also be achieved by other means.

As already explained, the dispersing unit 20 serves to distribute the product to be separated as homogeneously as possible in a carrier gas stream. For this, the in Fig. 2 schematically shown dispersing unit 20 described, wherein differently constructed dispersing units can also be used.

To generate the carrier gas stream into which the preliminary and intermediate product is introduced, a fan 45 with corresponding control is provided downstream of the filter 30. This blower 45 sucks the carrier gas through the filter 30, the multicyclone 1 and the dispersing unit 20.

For this purpose 20 air intake openings 23 are provided in the dispersing unit. The dispersing unit 20 itself has a distributor plate 22, a blade ring 24, turbulence internals 25 and a displacement body 26. The preliminary or intermediate product fed to the dispersing unit 20 via the screw conveyor 44 falls onto the distributor plate 22. The distributor plate 22 rotates, so that the applied preliminary or intermediate product slides laterally from the distributor plate 22 or is thrown against a wall of the dispersing unit 20. It is mechanically torn apart and distributed over a larger flow cross-section. The previously described carrier gas, which flows through the air intake openings 23 and is additionally swirled by means of the blade ring 24, which is arranged on the edge of the distributor plate 22, entrains the preliminary or intermediate product to be separated from the carrier gas stream. As a result of the rapidly flowing carrier gas, the preliminary or intermediate product is again torn apart, in this case pneumatically.

In order to achieve an even better dispersion, turbulence internals 25 are provided in the direction of flow of the carrier gas, which achieve additional turbulence and thus better dispersion of the preliminary and intermediate product to be separated. The turbulence internals 25 can be formed, for example, by means of static mixing elements or impact bodies. However, there is also the possibility, in addition or as an alternative to these versions, of using a dynamic rotor which further improves the mixing and dispersion of the preliminary or intermediate product. This is additionally improved by the displacement body 26, which can be designed to be height-adjustable.

After the dispersing unit 20, the preliminary or intermediate product to be separated is passed to the multicyclone 1 according to the invention by means of the carrier gas stream. This is, as already in relation to Fig. 1 explained, regulated in the basic state with regard to the loading of the carrier gas stream, which is set by means of the feed from the bunker 42, and the volume per unit time of the carrier gas stream, which is set via the blower 45, is operated in such a way that in the initial state an almost complete separation of the fine and very fine grain in the multicyclone 1 is made possible. A poorer separation is then achieved by supplying cyclone control air via the cyclone control air supply 9, so that the finer particles in the carrier gas stream are not separated as cyclone semolina, but instead are conducted further in the direction of the filter 30 with the carrier gas stream.

The fine particles are also separated in this filter 30 and can be removed from the filter 30, for example via a cellular wheel sluice 31. The carrier gas stream thus cleaned can in part be fed back into the process or blown out into the environment.

An advantage of the fine grain separator 40 described here is that it can always be operated in the range of an optimal operating point, regardless of upstream processes that produce the preliminary or intermediate product, since both the loading and the volume per unit of time of the carrier gas depend only on the properties of the individual assemblies of the finest grain separator 40 are defined and there is no need to take into account upstream or downstream further processes.

This is in relation to below Fig. 3 further clarified. In Fig. 3 a grinding plant 50 with a mill-sifter combination 51 is shown. The mill-sifter combination has a mill 52 and a sifter 53. The ground material crushed in the mill-sifter combination 51 is transported to a grinding plant filter 55 by means of a grinding plant carrier gas stream which is set by the mill blower 56. The grinding plant carrier gas stream can in part be returned via a hot gas generator 57, which, for example, enables grinding drying in the mill-sifter combination.

Particles which are in the carrier gas stream of the grinding plant are separated in the grinding plant filter 55. These particles are then fed to the finest grain separator 40 using a multicyclone 1 according to the invention.

This figure shows that the construction of the fine grain separator 40 according to the invention means that it can be operated essentially decoupled from the grinding plant circuit. As a result, both the grinding system 50 itself as well as the finest grain separator 40 can each be operated at optimal operating points which also depend on the loading of the carrier gas streams with material to be comminuted or material to be separated and the volume per unit time of the carrier gas.

Conventional grinding plants 50, as shown in FIGS Fig. 3 are exemplified, in their optimal operating point usually a loading of the carrier gas in the range of 30 g / m ³ to 50 g / m ³ with a fineness of up to 6000 cm ² / g. On the other hand, a multicyclone 1 according to the invention and thus also the finest grain separator 40 can be operated with a loading in the range between 200 g / m ³ to 300 g / m ³ . The decoupling makes it possible to make the fine grain separator 40 smaller, or to provide only one fine grain separator 40 for several grinding plants 50. This reduces the size of the system and thus minimizes the investment costs.

In Fig. 4 a combined schematic diagram is shown, which shows the relationship between the cyclone control air volume and the dust loading of the carrier gas in relation to the fineness of the fine grain.

The fineness in cm ² / g of the finest grain is provided on the ordinate. On the abscissa the cyclone control air volume in m ³ / h is shown on the left side and the loading of the carrier gas in g / m ³ on the right side.

As can be seen from the diagram, the fineness of the fine grain decreases with increasing cyclone control air volume. In contrast, an optimum of the dust loading or particle loading of the carrier gas stream upstream of the multicyclone is formed for the fineness.

From this it can be concluded that, as already described above, there is an optimal operating point for operating a multicyclone according to the invention in relation to the loading of the carrier air stream. The fineness of the fine grain can then be influenced according to a regulation via the cyclone control air.

The multicyclone according to the invention and its operating method for separating fine and very fine grain thus enable simple and efficient separation of fine and very fine grain as well as a decoupled operation to upstream process plants.

Claims (15)

1. Method for operating a multi-cyclone (1) for separating fine and very fine particles, whereby the multi-cyclone (1) comprises:

   several essentially identically designed individual cyclones (10), each of which features a carrier gas inlet opening (11), a carrier gas outlet opening (12) and a grit discharge opening (13),

   whereby the individual cyclones are housed together in a low-infiltrated-air housing (3), in which an upper (5) and a lower (6) chamber is designed,

   whereby the carrier gas outlet openings (12) of the individual cyclones (10) are open towards the upper chamber (5),

   whereby the upper chamber (5) has a carrier gas overall outlet opening (7) to discharge the carrier gas which enters the upper chamber (5) from the respective carrier gas outlet openings (12) of the individual cyclones (10), via the carrier gas overall outlet opening (7) from the housing (3) of the multi-cyclone (1).

   whereby the grit discharge openings (13) are each open designed towards the lower chamber (6),

   whereby the lower chamber (6) has a device (8) for the extraction of cyclone grits introduced through the grit discharge openings (13), which is realized largely free from infiltrated air,

   whereby a common cyclone control air supply (9) is provided to the lower chamber (6),

   wherein the carrier gas inlet openings (11) are each supplied from outside the housing (3) with a carrier gas flow of equal volume with the fine and very fine particles to be separated,
   wherein in the individual cyclones (10), an at least proportional separation of fine and very fine particles is carried out,
   wherein the fine particles enter the lower chamber (6) as cyclone grit via the grit discharge openings (13) and are discharged from there out of the housing (3) via the device (8) for extraction,
   whereby the very fine particles are passed as cyclone fines through the upper chamber (5) and the carrier gas overall outlet opening (7) out of the multi-cyclone (1) by means of the carrier gas flow,
   characterized in that
   by controlling the quantity of the cyclone control air per unit of time supplied by the cyclone control air fed (9) into the lower chamber (6), the quantity, the fineness, and/or the purity of the very fine particles fed from the multi-cyclone (1) is adjusted.
2. Method according to claim 1,
   characterized in that
   the volume per unit of time of the carrier gas flows of equal volume to the individual cyclones (10) is adjusted depending on the geometry of the individual cyclones (10), in order to separate approx. 99% of the fine and very fine particles being in the carrier gas flows as cyclone grit when the cyclone control air supply (9) is closed.
3. Method according to claim 1 or 2,
   characterized in that
   the load of the carrier gas flows of equal volume to the individual cyclones (10) with fine and very fine particles is adjusted depending on the geometry of the individual cyclones (10), in order to separate approx. 99% of the fine and very fine particles being in the carrier gas flows as cyclone grit when the cyclone control air supply (9) is closed.
4. Method according to one of claims 1 to 3,
   characterized in that
   a pressure difference between the upper (5) and lower (6) chamber is set during operation, and
   that the pressure in the upper chamber (5) is lower than the pressure in the lower chamber (6).
5. Method according to one of claims 1 to 4,
   characterized in that
   the pressure in the upper chamber (5) and in the lower chamber (6) is set lower than the ambient pressure.
6. Method according to one of claims 1 to 5,
   characterized in that
   the fine and very fine particles to be separated are fed to a dispersing unit (20), before the feed in the multi-cyclone (10) and from there are transported to the multi-cyclone (1) by means of the carrier gas flow.
7. Method according to one of claims 1 to 6,
   characterized in that
   the carrier gas flow with the very fine particles from the carrier gas overall outlet opening (7) is fed to a filter (30) for separating the very fine particles from the carrier gas flow.
8. Multi-cyclone (1) with
   several essentially identically designed individual cyclones (10), with in each case have a carrier gas inlet opening (11), a carrier gas outlet opening (12) and a grit discharge opening (13).
   whereby the individual cyclones (10) are housed together in a low-infiltrated-air housing (3), in which an upper (5) and a lower (6) chamber is designed, whereby the carrier gas outlet openings (12) of the individual cyclones (10) are designed open towards the upper chamber (5),
   whereby the upper chamber (5) has a carrier gas overall outlet opening (12) to discharge the carrier gas which enters the upper chamber from the respective carrier gas outlet openings (12) of the individual cyclones (10), via the carrier gas overall outlet opening (12) from the housing (3) of the multi-cyclone (10),
   whereby the grit discharge openings (13) in each case are designed open towards the lower chamber (6),
   whereby the lower chamber (6) has a device (8) for the extraction of grits introduced through the grit discharge openings (13), which is realized largely free from infiltrated air,
   whereby the carrier gas inlet openings (11) are each designed to be supplied from outside the housing (3) with a carrier gas flow of equal volume, which contains fine and very fine particles to be separated,
   characterized in that
   a common cyclone control air supply (9) is provided to the lower chamber (6), via which control air can be directed selectively into the lower chamber (6),
   that a control and regulating device is provided to adjust the quantity, the fineness, and/or the purity of the very fine particles directed from the multi-cyclone (1) by means of the quantity of the cyclone control air per unit of time, and
   that fine particles can be separated as cyclone grit.
9. Multi-cyclone according to claim 8,
   characterized in that
   the individual cyclones (10) are provided in the housing (3) in parallel, flow-wise.
10. Multi-cyclones according to claim 8 or 9,
    characterized in that
    the upper (5) and the lower (6) chambers are designed to be airtight to each other, whereby an air exchange between the upper chamber (5) and the lower chamber (6) only takes place via the individual cyclones (10).
11. Very fine particle separator (40) for separating fine and very fine particles from a preliminary or intermediate product with
    at least one multi-cyclone (1) according to one of claims 8 to 10 and a filter (30), whereby the preliminary or intermediate product can be supplied to the at least one multi-cyclone (1) by means of a carrier gas flow,
    whereby the fine particles can be separated on the multi-cyclone (1), and
    whereby by means of carrier gas the very fine particles can be further directed to the filter (30) and separated there.
12. Very fine particle separator (40) according to claim 11,
    characterized in that
    several multi-cyclones (1) are provided in series, flow-wise, one after another upstream of the filter (30) and
    the individual cyclones (10) of the multiple multi-cyclones (1) each feature a smaller diameter in the flow direction of the carrier gas flow.
13. Very fine particle separator (40) according to claim 11 or 12,
    characterized by
    a storage hopper (42) for the preliminary and intermediate product and a dispersing unit (20),
    whereby the preliminary or intermediate product to be separated is fed from the storage hopper (42) via the dispersing unit (20) to the very fine particle separator (40) by means of the carrier gas flow.
14. Grinding plant (50) to produce fine and very fine particles from a raw material with a mill-sifter combination (51), which features a sifter (53) and a mill (52),
    whereby the mill-sifter combination (51) is designed to feed raw material ground at least once during an initial sifting from the sifter (53) of the mill-sifter combination (51) back again to the mill (52) as rejected coarse material for further grinding, with a grinding plant filter (55),
    whereby by means of a grinding plant carrier gas flow, ground material not rejected by the sifter (53) of the mill-sifter combination (51) can be transported to the grinding plant filter (55), and there it can be separated from the grinding plant carrier gas flow,
    characterized by
    a very fine particle separator (40) according to one of the claims 11 to 13,
    whereby at least a part of the ground product separated on the grinding plant filter (55) can be fed to the very fine particle separator (40) as preliminary or intermediate product for the separation of fine and very fine particles.
15. The grinding plant according to claim 14,
    characterized in that
    the mill (52) of the mill-sifter combination (51) is a vertical mill with a grinding table and grinding rollers.

Images