EP2024093B1 - Method for producing very fine particles by means of a jet mill - Google Patents

Abstract

The invention relates to a method for producing very fine particles by means of a jet mill using compressed gases as the grinding gas, characterized in that the grinding gas is under pressure of ≰4.5 bar(abs).

Description

The present invention relates to a method for producing finest particles by means of a jet mill.

The material to be sighted or ground consists of coarser and finer particles which are entrained in an air stream and form the product stream which is introduced into a housing of a wind sifter of the jet mill. The product flow passes in the radial direction into a classifying wheel of the air classifier. In the classifying wheel, the coarser particles are eliminated from the air stream and the air stream leaves the classifying wheel with the fine particles axially through a discharge pipe. The air flow with the fine particles to be filtered out or produced can then be supplied to a filter in which a fluid, such as air, and fine particles are separated from each other.

From the DE 198 24 062 A1 Such a jet mill is known, in the grinding chamber further at least one high-energy jet jet of hot steam with high flow energy is introduced, wherein the grinding chamber except the inlet means for the at least one grinding jet has an inlet for the material to be ground and an outlet for the product, and wherein in the area of the coincidence of regrind and at least one grinding jet of hot steam and millbase have at least about the same temperature.

Furthermore, a corresponding air classifier, in particular for a jet mill, for example, from EP 0 472 930 B1 known. This air classifier and its operating methods are basically extremely satisfactory.

From the EP0211117 is an air classifier known in which compressed gases are used with pressures of up to 6.2 bar.

The present invention therefore has the aim of further optimizing a method for producing very fine particles by means of a jet mill.

This object is achieved by a method for producing very fine particles according to claim 1.

Accordingly, a method for producing very fine particles by means of a jet mill using compressed gases as the grinding gas is characterized in that the grinding gas has a pressure of ≤ 4.5 bar (abs).

This advantageously creates a process for the energy-optimized operation of a jet mill by means of compressed gases.

A preferred development is that the grinding gas is subjected to a jet milling of inorganic substances.

The method may preferably be further developed in that the temperature of the ground gas is> 100 ° C, wherein it is provided in particular that the temperature of the ground gas in the range of about 180 ° C to about 200 ° C.

• dass zunächst der spezifische adiabate Energieverbrauch eines Mahlprozesses unter Anwendung eines Mahlgasdruckes von > 7 bar(abs) ermittelt wird,
• dass dann der spezifische adiabate Energieverbrauch desselben Mahlprozesses unter Anwendung eines Mahlgasdruckes von < 4,5 bar(abs) ermittelt wird, und
• dass die beiden Energieverbräuche miteinander verglichen werden und in dem Fall $${\mathrm{E}}_{\mathrm{ad}\mathrm{,}\mathrm{spez}}\left(\mathrm{4},\mathrm{5}\right)\mathrm{\le }{\mathrm{E}}_{\mathrm{ad}\mathrm{,}\mathrm{spez}}\left(7\right)$$
  
  
  der Niederdruckbereich gewählt wird.

Furthermore, it can be provided with preference in the method,

• that first the specific adiabatic energy consumption of a milling process is determined using a grinding gas pressure of> 7 bar (abs),
• that then the specific adiabatic energy consumption of the same grinding process is determined using a grinding gas pressure of <4.5 bar (abs), and
• that the two energy consumptions are compared with each other and in the case $${\mathrm{e}}_{\mathrm{ad}\mathrm{.}\mathrm{spec}}\left(\mathrm{4},\mathrm{5}\right)\mathrm{\le }{\mathrm{e}}_{\mathrm{ad}\mathrm{.}\mathrm{spec}}\left(7\right)$$
  
  
  the low pressure range is selected.

Preferably, a fluid bed jet mill or a dense bed jet mill is used.

The determination of the two energy consumptions and their comparison preferably takes place at each start of operation or resumption of operation of the jet mill. It is particularly advantageous if the determination of the two energy consumptions and their comparison is carried out automatically. It is particularly advantageous if an operating mode setting also takes place automatically according to the result of the comparison.

It is also preferred to use a dynamic air classifier integrated in the jet mill. In this case, it is preferably further provided that the air classifier contains a classifying rotor or a classifying wheel with a clear height which increases with decreasing radius, so that when Operation is the flow-through surface of the classifying rotor or wheel at least approximately constant. Alternatively or additionally, it can be provided that the air classifier contains a classifying rotor or a classifying wheel with a particularly exchangeable dip tube which is designed such that it rotates when the classifying rotor or the classifying wheel rotates.

Yet another preferred embodiment of the method is that a fine-material outlet chamber is provided, which has a cross-sectional widening in the flow direction.

Preferred and / or advantageous embodiments of the invention will become apparent from the claims and their combinations as well as the entire present application documents.

Fig. 1

diagrammartig ein Ausführungsbeispiel einer Strahlmühle in einer teilweise ge- schnittenen Schemazeichnung zeigt,

Fig. 2

ein Ausführungsbeispiel eines Windsichters einer Strahlmühle in vertikaler An- ordnung und als schematischer Mittellängsschnitt zeigt, wobei dem Sichtrad das Auslassrohr für das Gemisch aus Sichtluft und Feststoffpartikeln zugeordnet ist, und

Fig. 3

in schematischer Darstellung und als Vertikalschnitt ein Sichtrad eines Windsich- ters zeigt.

The invention will be explained in more detail by way of example only with reference to exemplary embodiments, with reference to the drawings, in which:

Fig. 1

shows diagrammatically an exemplary embodiment of a jet mill in a partially sectioned schematic drawing,

Fig. 2

shows an embodiment of an air classifier of a jet mill in a vertical arrangement and as a schematic central longitudinal section, wherein the classifying wheel is associated with the outlet pipe for the mixture of classifying air and solid particles, and

Fig. 3

shows in schematic representation and as a vertical section a classifying wheel of a wind sensor.

With reference to the embodiments and application examples described below and illustrated in the drawings, the invention will be explained only by way of example, i. it is not limited to these embodiments and applications or to the respective combinations of features within individual examples of embodiments and applications. Process and device features result analogously also from device or process descriptions.

Individual features that are indicated and / or illustrated in connection with specific embodiments are not limited to these embodiments or the combination with the other features of these embodiments, but may in the context of the technical possibility, with any other variants, even if they are not treated separately in the present documentation.

The same reference numerals in the individual figures and illustrations of the drawings designate the same or similar or identical or similar components. On the basis of the representations in the drawing, those features are also clear, which are not provided with reference numerals, regardless of whether such features are described below or not. On the other hand, features that are included in the present description but are not visible or illustrated in the drawing will be readily understood by those skilled in the art.

In the method for producing finest particles by means of a jet mill, the new steps provided by the present invention are so clear and understandable that a graphical representation of the individual steps is unnecessary.

In the method for producing finest particles by means of a jet mill using compressed gases as the grinding gas is provided in the core that the grinding gas has a pressure of ≤ 4.5 bar (abs). This advantageously creates a process for the energy-optimized operation of a jet mill by means of compressed gases.

A preferred development is that the grinding gas is subjected to a jet milling of inorganic substances. The method may preferably be further developed in that the temperature of the ground gas is> 100 ° C, wherein it is provided in particular that the temperature of the ground gas in the range of about 180 ° C to about 200 ° C.

Furthermore, it is in the inventive sense in the method for energetically optimized operation of a jet mill, such as a fluidized bed jet mill to design by compressed gases in a further preferred manner, the specific adiabatic energy consumption of a milling process using a Mahlgasdruckes of> 7 bar (abs) is first determined for which purpose suitable sensors and processor devices which are known to the person skilled in the art are used, so that their design need not be discussed further here. Advantageously, a takeover of the thus obtained value of the specific adiabatic energy consumption takes place at a grinding gas pressure of> 7 bar (abs) in a memory. Thereafter, using the same sensors and processor means, the specific adiabatic energy consumption of the same milling process is determined using a milling gas pressure of <4.5 bar (abs). Preferably, this value of the specific adiabatic energy consumption at a Mahlgasdruck of <4.5 bar (abs) in a Memory read. Now, the two energy consumptions are compared, for example, by means of the already used for the determination of the energy consumption itself or other processor devices and is in the case $${\mathrm{e}}_{\mathrm{ad}\mathrm{.}\mathrm{spec}}\left(\mathrm{4},\mathrm{5}\right)\mathrm{\le }{\mathrm{e}}_{\mathrm{ad}\mathrm{.}\mathrm{spec}}\left(7\right)$$

the low pressure range selected for the operation of the jet mill. In addition to the fact that the corresponding operating mode can be set manually in accordance with the result of the comparison, which is visually indicated by suitable known devices, an automatic adjustment of the corresponding operating mode according to the result of the comparison is also possible if a suitable control exists and, on the one hand, determines the result of the comparison Processor means and on the other hand control means is connected, so that the control in response to the result of the comparison in accordance with the processor means causes the control means for setting the corresponding operating mode.

The method according to the invention is preferably carried out before each new operation of the jet mill, in particular with new ground material, and is thus part of the overall operating method of the jet mill.

It is also preferred to use a dynamic air classifier integrated in the jet mill. In this case, it is preferably further provided that the air classifier contains a classifying rotor or a classifying wheel with a clear height increasing with decreasing radius, so that the area of the classifying rotor or wheel through which flows is at least approximately constant during operation. Alternatively or additionally, it can be provided that the air classifier contains a classifying rotor or a classifying wheel with a particularly exchangeable dip tube which is designed such that it rotates when the classifying rotor or the classifying wheel rotates.

Yet another preferred embodiment of the method is that a fine-material outlet chamber is provided, which has a cross-sectional widening in the flow direction.

In the Fig. 1 an embodiment of a jet mill 1 for carrying out the method explained above is shown schematically. As already explained above, the method according to the invention can be carried out manually or automatically, which has no fundamental influence on the usefulness of the method. The automated version of course allows a further reduction of the effort and is easy can be realized with means and means known to the person skilled in the art, which, however, is not intended to indicate that the person skilled in the art would also be aware of the individual steps of the method newly created by the present invention. In any case, dealing with the sensor, measuring, processor, storage and control devices and control in general and in particular unnecessary, since this device implementation of the method according to the invention does not require its own inventive steps in the knowledge thereof.

The jet mill 1 according to the Fig. 1 contains a cylindrical housing 2, which encloses a grinding chamber 3, a Mahlgutaufgabe 4 approximately half the height of the grinding chamber 3, at least one Mahlstrahleinlass 5 in the lower region of the grinding chamber 3 and a product outlet 6 in the upper region of the grinding chamber 3. There is an air classifier with a rotatable classifying wheel 8, with which the material to be ground (not shown) is classified in order to remove only material to be ground below a certain particle size through the product outlet 6 from the grinding chamber 3 and feed grinding material having a particle size above the selected value to a further grinding operation.

The classifying wheel 8 can be a classifying wheel which is common in air classifiers and whose blades (see later eg in connection with FIG Fig. 3 ) define radially extending blade channels, at the outer ends of which the classifying air enters and entrains particles of smaller grain size or mass to the central outlet and to the product outlet 6, while larger particles or particles of larger mass are rejected under the influence of centrifugal force. In particular, the air classifier 7 and / or at least its classifying wheel 8 with at least one design feature according to the EP 0 472 930 B1 fitted.

It can be provided only a Mahlstrahleinlass 5, for example, consisting of a single, radially directed inlet opening or inlet nozzle 9 to impinge a single grinding jet 10 on the Mahlgutpartikel that come from the Mahlgutaufgabe 4 in the area of the grinding jet 10, with high energy and the To allow regrind particles to be broken down into smaller sub-particles, which are sucked in by the classifying wheel 8 and, insofar as they have a correspondingly small size or mass, are conveyed through the product outlet 6 to the outside. However, a better effect is achieved with pairwise diametrically opposed Mahlstrahleinlässen 5, which form two colliding grinding jets 10, which cause the particle separation more intense than is possible with only one grinding jet 10, especially when multiple Mahlstrahlpaare are generated.

Furthermore, for example, the processing temperature can be influenced by using an internal heat source 11 between Mahlgutaufgabe 4 and the range of grinding jets 10 or a corresponding heat source 12 in the area outside the Mahlgutaufgabe 4 or by processing particles of already warm ground material, while avoiding heat loss in the Mahlgutaufgabe 4 passes, to which a feed tube 13 is surrounded by a temperature-insulating jacket 14. The heating source 11 or 12 may, when used, be basically arbitrary and therefore purposely operational and selected according to market availability, so that further explanation is not required.

For the temperature, in particular the temperature of the grinding jet or the grinding jets 10 is relevant and the temperature of the material to be ground should at least approximately correspond to this grinding jet temperature.

To form the grinding jets 10 introduced into the grinding chamber 3 by grinding jet inlets 5, it is possible, for example, to use superheated steam as well as any other suitable fluid. When using superheated steam, it can be assumed that the heat content of the steam after the inlet nozzle 9 of the respective Mahlstrahleinlasses 5 is not significantly lower than in front of this inlet nozzle 9. Because the energy required for the impact crushing is primarily to be available as flow energy, on the other hand Pressure drop between the inlet 15 of the inlet nozzle 9 and the outlet 16 be considerable (the pressure energy will be largely implemented in flow energy) and also the temperature drop will not be negligible. In particular, this temperature drop is to be compensated so far by the heating of the ground material that regrind and grinding jet 10 in the region of the center 17 of the grinding chamber 3 at least two colliding grinding jets 10 or a multiple of two grinding jets 10 have the same temperature.

For the design and implementation of the preparation of the grinding jet 10 from superheated steam, in particular in the form of a closed system is on the DE 198 24 062 A1 Reference is made in its entirety to the entire contents of this disclosure for the purpose of avoiding merely identical assumption. By a closed system, for example, a grinding of hot slag as regrind with optimum efficiency is possible.

In the representation of the present embodiment of the jet mill 1 is representative of any supply of a resource or medium B, a reservoir or generating means 18, such as a tank 18 a shown, from which the resources or operating medium B via line means 19 to the grinding jet inlet 5 or the Mahlstrahleinlässen 5 to the formation of the grinding jet 10 and the grinding jets 10 is passed. Instead of the tank 18 a, for example, a compressor can be used to provide appropriate operating medium B available.

In particular, starting from a jet mill 1 equipped with such an air classifier 7, the relevant exemplary embodiments being intended and to be understood here only as an example and not as a limitation, a method for producing extremely fine particles is carried out with this jet mill 1 with an integrated dynamic air classifier 7. As the resource B, a fluid is generally used, preferably the water vapor already mentioned, but also hydrogen gas or helium gas or simply air.

Furthermore, it is advantageous and therefore preferred if the classifying rotor 8 has a clear height which increases with decreasing the radius, that is to say towards its axis, wherein in particular the area of the classifying rotor 8 through which it flows is constant. Additionally or alternatively, a fine-material outlet chamber (not shown) may be provided which has a cross-sectional widening in the flow direction.

A particularly preferred embodiment of the jet mill 1 is that the sifting rotor 8 has an exchangeable, co-rotating dip tube 20.

Only to explain and to deepen the overall understanding will be discussed below on the particles to be produced from the preferably processed material. For example, these are amorphous SiO ₂ or other amorphous chemical products which are comminuted with the jet mill. Other materials include silicic acids, silica gels or silicates or materials based on or containing carbon black.

The following are with reference to the Fig. 2 and 3 further details and variants of exemplary embodiments of the jet mill 1 and its components explained.

The jet mill 1 contains, as the schematic representation in the Fig. 2 It can be seen, an integrated air classifier 7, which is for example in types of jet mill 1 as fluidized bed jet mill or as a dense bed jet mill to a dynamic air classifier 7, which is advantageously arranged in the center of the grinding chamber 3 of the jet mill 1. Depending on the grinding gas volume flow and classifier speed, the desired fineness of the material to be ground can be influenced.

In the air classifier 7 of the jet mill 1 according to the Fig. 2 the entire vertical air classifier 7 is enclosed by a classifier housing 21, which consists essentially of the upper housing part 22 and the lower housing part 23. The upper housing part 22 and the lower housing part 23 are provided at the upper or lower edge, each with an outwardly directed peripheral flange 24 and 25 respectively. The two peripheral flanges 24, 25 are in the installation or functional state of the air classifier 8 on each other and are fixed by suitable means against each other. Suitable means for fixing are, for example, screw connections (not shown). As releasable fastening means may also serve brackets (not shown) or the like.

At a virtually arbitrary point of the flange circumference, both circumferential flanges 24 and 25 are connected to one another by a hinge 26 so that the upper housing part 22 can be pivoted upward in the direction of the arrow 27 after loosening the flange connecting means relative to the lower housing part 23 and the upper housing part 22 from below and the lower housing part 23 are accessible from above. The lower housing part 23 in turn is formed in two parts and it consists essentially of the cylindrical Sichtraumgehäuse 28 with the peripheral flange 25 at its upper open end and a discharge cone 29, which tapers conically downwards. The discharge cone 29 and the Sichtraumgehäuse 28 are at the upper and lower ends with flanges 30, 31 on each other and the two flanges 30, 31 of discharge cone 29 and Sichtraumgehäuse 28 are like the peripheral flanges 24, 25 connected by releasable fastening means (not shown). The thus assembled classifier housing 21 is suspended in or on support arms 28a, of which a plurality of evenly spaced around the circumference of the classifier or compressor housing 21 of the air classifier 7 of the jet mill 1 are distributed and attack the cylindrical Sichtraumgehäuse 28.

An essential part of the housing installations of the air classifier 7 is in turn the classifying wheel 8 with an upper cover plate 32, with an axially spaced lower downstream cover plate 33 and arranged between the outer edges of the two cover plates 32 and 33, fixedly connected to these and evenly around the circumference of Classifying wheel 8 distributed blades 34 with appropriate contour. In this air classifier 7, the drive of the classifying wheel 8 is effected via the upper cover disk 32, while the lower cover disk 33 is the downstream cover disk. The storage of the classifying wheel 8 comprises a positively driven forcibly Sichtradwelle 35, which is led out with the upper end of the classifier housing 21 and rotatably supports the classifying wheel 8 with its lower end within the classifier housing 21 in flying storage. The exit of the Sichtradwelle 35 from the classifier housing 21 takes place in a pair of machined plates 36, 37 which terminate the classifier housing 21 at the upper end of an upwardly frusto-conical housing end portion 38 guiding the classifying wheel shaft 35 and sealing this shaft passage without obstruction of the rotational movements of the classifying wheel shaft 35. Conveniently, the upper plate 36 can be rotatably associated with the Sichtradwelle 35 as a flange and rotatably supported via pivot bearings 35a on the lower plate 37, which in turn is associated with a housing end portion 38. The underside of the downstream cover disk 33 lies in the common plane between the peripheral flanges 24 and 25, so that the classifying wheel 8 is arranged in its entirety within the hinged housing upper part 22. In the region of the conical housing end portion 38, the upper housing part 22 also has a tubular product feed nozzle 39 of the Mahlgutaufgabe 4, the longitudinal axis parallel to the axis of rotation 40 of the classifying wheel 8 and its drive or Sichtradwelle 35 and as far as possible from this axis of rotation 40 of the classifying wheel 8 and its Drive or Sichtradwelle removed 35, the housing upper part 22 is disposed radially outboard.

The classifier housing 21 receives the coaxial with the classifying wheel 8 arranged tubular outlet nozzle 20 which lies with its upper end just below the downstream cover plate 33 of the classifying wheel 8, but without being connected thereto. At the lower end of the tube formed as a discharge nozzle 20, an outlet chamber 41 is attached coaxially, which is also tubular, but whose diameter is substantially greater than the diameter of the outlet nozzle 20 and in the present embodiment, at least twice as large as the diameter of the outlet nozzle 20. At the transition between the outlet nozzle 20 and the outlet chamber 41 so there is a significant diameter jump. The outlet nozzle 20 is inserted into an upper cover plate 42 of the outlet chamber 41. Below the outlet chamber 41 is closed by a removable cover 43. The assembly of outlet nozzle 20 and outlet chamber 41 is held in a plurality of support arms 44 which are evenly distributed star-shaped around the circumference of the unit, connected with their inner ends in the region of the outlet nozzle 20 fixed to the unit and secured with their outer ends on the classifier housing 21.

The outlet nozzle 20 is surrounded by a conical annular housing 45 whose lower, larger outer diameter corresponds at least approximately to the diameter of the outlet chamber 41 and its upper, smaller outer diameter at least approximately the diameter of the classifying wheel 8. At the conical wall of the ring housing 45, the support arms 44 terminate and are firmly connected to this wall, which in turn is part of the assembly of outlet nozzle 20 and outlet chamber 41.

The support arms 44 and the annular housing 45 are parts of a scavenging air device (not shown), wherein the scavenging air prevents the ingress of matter from the interior of the classifier housing 21 into the gap between the classifying wheel 8 or more precisely its lower cover disk 3 and the outlet nozzle 20. In order to get this scavenging air into the ring housing 45 and from there into the gap to be kept clear, the support arms 44 are formed as tubes, with their outer end portions passed through the wall of the classifier housing 21 and connected via a suction filter 46 to a purge air source (not shown) , The annular housing 45 is closed at the top by a perforated plate 47 and the gap itself can be adjusted by an axially adjustable annular disc in the area between the perforated plate 47 and the lower cover plate 33 of the classifying wheel 8.

The outlet from the outlet chamber 41 is formed by a fines discharge pipe 48, which is led into the separator housing 21 from the outside and is connected in a tangential arrangement to the outlet chamber 41. The fine material discharge pipe 48 is part of the product outlet 6. The lining of the junction of the fine material discharge pipe 48 with the outlet chamber 41 serves as a deflecting cone 49.

At the lower end of the conical housing end section 38, a sighting air inlet spiral 50 and a coarse material discharge 51 are assigned to the housing end section 38 in a horizontal arrangement. The direction of rotation of the sighting air inlet spiral 50 is opposite to the direction of rotation of the classifying wheel 8. The coarse material discharge 51 is detachably associated with the housing end portion 38, the lower end of the housing end portion 38 is a flange 52 and the upper end of Grobgutaustrages 51 assigned a flange 53 and both flanges 52 and 53 are in turn releasably connected together by known means when the air classifier 7 is ready is.

The dispersing zone to be designed is designated 54. Flanges machined on the inner edge (chamfered) for a clean flow guidance and a simple lining are designated with 55.

Finally, a replaceable protective tube 56 is still applied to the inner wall of the outlet nozzle 20 as a wear part and a corresponding replaceable protective tube 57 may be applied to the inner wall of the outlet chamber 41.

At the beginning of the operation of the air classifier 7 in the illustrated operating state, view air is introduced into the air classifier 7 at a pressure gradient and at a suitably chosen entry speed via the sighting air inlet spiral 50. As a result of introduction the classifying air by means of a spiral, in particular in conjunction with the conicity of the housing end portion 38, the classifying air rises spirally upwards into the region of the classifying wheel 8. At the same time, the "product" of solid particles of different mass is introduced into the classifier housing 21 via the product feed port 39. From this product, the coarse material, ie the proportion of particles with a greater mass against the classifying air in the range of Grobgutaustrages 51 and is provided for further processing. The fine material, ie the particle fraction with a smaller mass is mixed with the classifying air, passes radially from outside to inside through the classifying wheel 8 into the outlet pipe 20, into the outlet chamber 41 and finally via a fine material outlet pipe 48 into a fine material outlet or outlet 58, as well as from there in a filter in which the resources in the form of a fluid, such as air, and fines are separated. Coarser Feingutbestandteile are radially ejected from the classifying wheel 8 and mixed with the coarse material to leave the classifier, housing 21 with the coarse material or to circle so long in the classifier housing 21 until it has become fines of such grain, that it with the classifying air is discharged.

As a result of the abrupt cross-sectional widening from the outlet nozzle 20 to the outlet chamber 41, there is a significant reduction in the flow velocity of the fine-material-air mixture. This mixture will therefore reach the fine material outlet 58 via the fine-material outlet pipe 48 at a very low flow rate through the outlet chamber 41 and produce abrasion only to a slight extent on the wall of the outlet chamber 41. Therefore, the protective tube 57 is only a highly precautionary measure. However, the reasons for a good separation technology high flow velocity in classifying wheel 8 still prevails in the discharge or outlet nozzle 20, which is why the protective tube 56 is more important than the protective tube 57. Particularly significant is the diameter jump with a diameter extension in the transition from the outlet nozzle 20 into the outlet chamber 41st

Incidentally, the air classifier 7 can again be well maintained by the division of the classifier housing 21 in the manner described and the assignment of the classifier components to the individual sub-housings and defective components can be replaced with relatively little effort and within short maintenance times.

While in the schematic representation of Fig. 2 the classifying wheel 8 with the two cover disks 32 and 33 and the blade ring 59 arranged therebetween with the blades 34 is shown in already known, conventional form with parallel and parallel-sided cover disks 32 and 33 Fig. 3 the classifying wheel 8 is shown for a further embodiment of the air classifier 7 of an advantageous development.

This classifying wheel 8 according to the Fig. 3 In addition to the blade ring 59 with the blades 34, the upper cover plate 32 and the axially spaced lower downstream cover plate 33 and is rotatable about the axis of rotation 40 and thus the longitudinal axis of the air classifier 7. The diametrical extent of the classifying wheel 8 is perpendicular to the axis of rotation 40, ie to the longitudinal axis of the air classifier 7, regardless of whether the axis of rotation 40 and thus said longitudinal axis is vertical or horizontal. The lower downstream cover disk 33 concentrically encloses the outlet nozzle 20. The blades 34 are connected to both cover disks 33 and 32. The two cover plates 32 and 33 are deviating now deviating from the prior art conical and was preferably such that the distance between the upper cover plate 32 from the downstream cover plate 33 from the rim 59 of the blades 34 inward, ie towards the axis of rotation 40 back, and Although preferably continuous, such as linear or non-linear, and with further preference so that the surface of the flow-through cylinder jacket for each radius between blade outlet edges and outlet nozzle 20 remains constant. The decreasing due to the decreasing radius in known solutions outflow rate remains constant in this solution.

Except for the above and in the Fig. 3 explained variant of the design of the upper cover plate 32 and the lower cover plate 33, it is also possible that only one of these two cover plates 32 or 33 is conical in the manner explained and the other cover plate 33 and 32 is flat, as in connection with the embodiment according to the Fig. 2 for both covers 32 and 33 is the case. In particular, the shape of the non-parallel-sided cover disk may be such that at least approximately so that the surface of the cylinder jacket through which flows through remains constant for each radius between blade outlet edges and outlet nozzle 20.

LIST OF REFERENCE NUMBERS

1

jet mill

2

cylindrical housing

3

grinding chamber

4

Mahlgutaufgabe

5

milling jet

6

product outlet

7

air classifier

8th

classifying wheel

9

Inlet opening or inlet nozzle

10

milling jet

11

heating source

12

heating source

13

feed pipe

14

temperature-insulating jacket

15

inlet

16

outlet

17

Center of the grinding chamber

18

Reservoir or generating device

19

line devices

20

outlet connection

21

classifier

22

Housing top

23

Housing bottom

24

circumferential flange

25

circumferential flange

26

joint

27

arrow

28

Classifying chamber housing

28a

carrying arms

29

discharge cone

30

flange

31

flange

32

cover disc

33

cover disc

34

shovel

35

classifying wheel shaft

35a

pivot bearing

36

upper machined plates

37

lower machined plate

38

housing end

39

Product feeding connection

40

axis of rotation

41

exit chamber

42

upper cover plate

43

removable lid

44

carrying arms

45

conical ring housing

46

Suction

47

perforated plate

48

Feingutaustragrohr

49

deflection cone

50

Air inlet spiral

51

coarse material

52

flange

53

flange

54

dispersing zone

55

flanges and lining machined on the inside edge (beveled)

56

replaceable thermowell

57

replaceable thermowell

58

Fines outlet / outlet

59

blade ring

Claims (13)

1. Method for producing very fine particles by means of a jet mill (1) using compressed gases as a grinding gas, characterised in that the grinding gas has a pressure of ≤ 4.5 bar(abs).
2. Method as claimed in Claim 1, characterised in that jet milling of inorganic substances occurs using the grinding gas.
3. Method as claimed in Claim 1 or 2, characterised in that the temperature of the grinding gas is 100°C.
4. Method as claimed in Claim 3, characterised in that the temperature of the grinding gas is in the range of approximately 180°C to approximately 200°C.
5. Method as claimed in any one of the preceding Claims, characterised in that

   - firstly, the specific adiabatic energy consumption of a grinding process is determined using a grinding gas pressure of> 7 bar(abs),

   - then, the specific adiabatic energy consumption of the same grinding process is determined using a grinding gas pressure of< 4.5 bar(abs), and

   - the two energy consumptions are compared with each other and if $${\mathrm{E}}_{\mathrm{ad}\mathrm{,}\mathrm{spec}}\left(\mathrm{4.5}\right)\mathrm{\le }{\mathrm{E}}_{\mathrm{ad}\mathrm{,}\mathrm{spec}}\left(7\right)$$

   

   for the operation of the jet mill (1) the low pressure range is selected.
6. Method as claimed in Claim 5, characterised in that the determination of the two energy consumptions and the comparison thereof are performed during each operation start-up or operation resumption of the jet mill.
7. Method as claimed in Claim 6, characterised in that the determination of the two energy consumptions and the comparison thereof are performed in an automated manner.
8. Method as claimed in Claim 7, characterised in that an operation mode is set in an automated manner to the low pressure range or the high pressure range in accordance with the result of the comparison.
9. Method as claimed in any one of the preceding Claims, characterised in that a fluidised bed jet mill or a dense bed jet mill is used.
10. Method as claimed in any one of the preceding Claims, characterised in that a dynamic air classifier (7) integrated into the jet mill (1) is used.
11. Method as claimed in Claim 10, characterised in that the air classifier (7) contains a separator rotor or a separator wheel (8) with a clearance height which increases as the radius decreases so that during operation the surface area of the separator rotor or wheel (8) having a flow therethrough is at least approximately constant.
12. Method as claimed in Claim 10 or 11, characterised in that the air classifier (7) contains a separator rotor or a separator wheel (8) having a particularly replaceable immersion pipe (20) which is designed such that it rotates when the separator rotor or the separator wheel (8) rotates.
13. Method as claimed in any one of the preceding Claims, characterised in that a fine material outlet chamber (41) is provided which has a cross-sectional enlargement in the flow direction.

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