DE102010007004A1 - Method for filtering or screening of goods, involves glazing cryogenic medium to goods before filtering to cool goods, where nitrogen or carbon dioxide, particularly in form of carbon dioxide pallet or snow is used as cryogenic medium - Google Patents

Abstract

The method involves glazing a cryogenic medium to the goods before filtering or screening in order to cool the goods. Nitrogen or carbon dioxide, particularly in the form of carbon dioxide pallet or carbon dioxide snow is used as cryogenic medium. The carbon dioxide pallets are added in an amount such that they support the filtering of the goods through a filter (30) by rolling on the filtered goods. An independent claim is also included for a device for cooling of goods during filtering or screening.

Description

The present invention relates to a method for screening or sifting.

In the case of cryogenic fine grinding, cooling of the product causes an increase in the grinding capacity due to the embrittlement of the material and the reduction of the comminuting energy.

Cryogenic grinding processes increase product quality. Cubic shapes and smooth surfaces give the resulting powder during grinding an excellent flowability. Due to the thermal protection, all product-specific properties are preserved.

Composite materials that are suitable for recycling can in many cases be broken down into their constituents only with cryogenic grinding separation processes and comminuted. The cold of the gas causes embrittlement of the goods. Low energy consumption and a high product throughput make the processes attractive.

When recycling fiber composite materials, the cryogenic processes offer decisive advantages. While the thermoplastics are comminuted in powdered recyclate, the fibers form wool ball-like compounds, which can be separated by a subsequent screening.

Such methods ensure a high grinding performance, good flowability, a high degree of fineness, thermal damage to the material is avoided by the use of nitrogen or carbon dioxide.

By means of the resulting gas phase results in the grinding chamber reliable protection against fires and dust explosions by the inert gas atmosphere.

Cold grinding plants are divided into those with regrind embrittlement and those without them (direct feeding into the mill), if they are already brittle regrind materials. For example, cold grinding plants for spices and for thermoplastics are known.

In a cold grinding plant for spices, a spice to be ground, for example pepper, is stored in a storage container. About a rotary valve, the required amount of good is deducted. By feeding liquid nitrogen or carbon dioxide (CO ₂ ) to the material, it is ensured that the material does not become too hot due to the comminution heat in the mill. For relatively brittle materials such as pepper, a previous embrittlement is usually not required. Mills with and without sieve insert are used. A cellular wheel removes the regrind from the system. In this process, the gas mixture produced in the mill is removed by a filter for cleaning. The proportion of gas corresponding to the amount of gas introduced is released via a throttle valve. The remaining amount of gas (recycle gas) is returned to the mill. In this way, a gentle, dry and continuous grinding operation is possible. The controlled, low temperature prevents adhesion of the ground product in the grinding plant.

Substances such as thermoplastics often have to be embrittled before grinding. In a cold grinding plant for thermoplastics, a cellular wheel doses a plastic granulate, for example polyethylene (PE) or polyamide (PA), into the grinding plant. The grinding heat would melt many thermoplastics in the mill and would therefore no longer be grindable. The cold of the liquid nitrogen embrittles the material already in a cooling device upstream of the mill (eg cooling screw, rotary tube cooler or cooling tower) in such a way that it can not melt during the grinding process. A rotary feeder removes the shredded product for further processing. The resulting gas mixture in the mill is previously passed through a filter for cleaning. The proportion of gas corresponding to the amount of nitrogen introduced is released. The remaining amount of gas is fed back to the mill for residual refrigeration.

If the previous regrind embrittlement is necessary, usually liquid nitrogen is used. If only the heat generated during the process has to be dissipated, liquid carbon dioxide or liquid nitrogen can be found. When the liquid carbon dioxide is injected, the expansion results in dry ice and cold, gaseous CO ₂ .

A sifter is a device for classifying solids according to defined criteria such as particle size, density, inertia and the floating or stratification behavior of substances.

In an air classifier, separation takes place in a stream of air, entraining the less dense and floatable particles.

For the separation of solid particles, which have the same density but different sizes, Plansichter can be used. In this case, the material to be separated is moved over vibrating screens, with the smaller particles sinking down and falling through the screen mesh.

In particle measurement, measuring cyclones, (cascade) impactors or beam deflection classifiers are used to classify gas-borne particles according to their size. Here, it is used that the particle web within the separation apparatus depends on the inertia of the particles.

A classifier mill is a combination of mill and classifier. The grinding and viewing process takes place in a housing. As a result, this type of mill builds extremely small. The product to be ground is fed into the machine in a stream of air and comminuted there. Fine particles pass through the classifying wheel and are exhausted by downstream equipment. Coarse particles are thrown back into the grinding chamber where they are further ground. The product is accelerated by bats and crushed when impacted on the grinding tracks (impact grinding).

In particular, fine-grained powders, such as those incurred during cold milling, can not be sieved by means of a simple mesh sieve without additional measures. Due to the small particle size of the powder and the associated low mass of the individual grains, the mass forces utilized during the sieving process are very small, so that disturbing influences, such as electrostatic charge and / or air currents and / or humidity, can extremely hinder the sieving. If the mass forces are too small, so that the disturbing influences predominate, a screening of a conventional kind is not feasible.

The particularly difficult to sieve powders include, in particular, electrostatically charged substances, for example plastic powders (for example polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polypropylene (PP), etc.). Also fabrics with fibrous grain shape, z. As tobacco dust, tea, leaf drugs, etc. prepare the sieving difficulties. Also problematic are substances with low specific gravity, such as carbon powder and graphite. Also problematic in the classification are sticky, greasy and lubricating products such as nutmeg or gum powder.

By means of grounded metallic screen mesh or by a low-air Siebdeckbewegung and by various sieve aids is trying to solve the problems described above. The screening aids include, for example, knocking balls which strike against the underside of the screening deck, or brushes which pass through the screenings through the stitches.

These methods, however, are associated with significant disadvantages. Thus, unusual bristles of the brushes or abrasion of the knocking balls can contaminate the sieve product. Also, the brushing brushes can destroy the mesh. In addition, a high proportion of fines still passes into the coarse material, ie. H. the so-called Fehlkornanteil is very high.

In the DE 41 07 872 A1 a method for screening a fine-grained material is described. In this method, it is provided that a coarse-grained substrate is added to the screenings before and / or during the screening process. Preferably, the substrate is a species-specific material with respect to the screenings. The coarse-grained substrate has a grain size which is significantly greater than the mesh size of the screen mesh, so that it is not subjected to screening itself. The much larger substrate particles act as screen aids for the very fine screenings particles and drive them, uninfluenced by electrostatics and draft through the screen meshes. This method can also be used in a cold grinding plant. In this case, the coarse-grained substrate is cooled before and / or during comminution by means of a cryogenic refrigerant.

Object of the present invention is to provide a method for screening or sizing, in which a size separation of a good is very effective, reliable and easy to execute.

The object is achieved by a method according to claim 1 and an apparatus according to claim 9. Advantageous embodiments are specified in the subclaims.

According to a first aspect of the method according to the invention for screening or sifting, a good is added to a good before or during sieving or sifting.

In the context of the present invention, a good is understood as meaning a substance or a material to be ground or a material to be screened or a material to be segregated which sifting through a sieve in a sieve device or when sifting through a viewing device undergoes size separation.

By means of the method according to the invention, a sieving or visual process can be carried out under a dry, cold and inert atmosphere. In this case, adhesion of the individual particles of the product to each other and to the components of a screening or viewing device is prevented because the components and the material are kept dry, cold and inert.

The cryogenic medium is nitrogen or carbon dioxide. Preferably, CO ₂ pellets and / or CO ₂ snow are used.

Since the sublimating gas from cryogenic medium is inert, the cryogenic medium can not alter the good or react with the good. Due to the residue-free sublimation to inert Gas, there are no unwanted effects, such. As contamination or mechanical abrasion.

Cooling with CO ₂ pellets has the advantage over cooling processes with liquid nitrogen or liquid CO ₂ or CO ₂ snow that the pellets sublime over a longer period of time and thus cool the material to be cooled longer. In this way, a refrigeration saving of 2% to 10% depending on the system is possible.

According to a second aspect of the present invention, in a process for screening a fine-grained material to be screened before and / or during the screening CO ₂ pellets fed, the CO ₂ pellets supported the screening of the screenings through a sieve by rolling on the Siebgut ,

By rolling the solid CO ₂ pellets on the estate, the small product particles of the goods are passed through the surface of a sieve or a sieve insert a screening device, so that they without screen help, such. B. balls or brushes can be discharged.

According to the second aspect of the method according to the invention is advantageous that the CO ₂ pellets supported the screening of the screenings through a sieve by rolling on the Siebgut and at the same time the Good cooling efficiently whereby an adhesion of the individual particles of Guts together and to the components of the device is prevented.

The much larger CO ₂ pellets act as screen aids for the very fine screenings particles and drive them, uninfluenced by electrostatics and draft through the screen meshes.

Since solid CO ₂ pellets and the subliming gas are inert, they can not change the screenings or react with the screenings. Since CO ₂ pellets sublime residue-free to inert CO ₂ gas, there is no mechanical abrasion of this screening aid.

According to the present invention, conventional CO ₂ pellets are used. Such CO ₂ pellets generally have a size of approximately 3 mm. The size of the CO ₂ pellets is understood to mean the length for rice grain-shaped CO ₂ pellets, and the diameter is meant for larger round CO ₂ pellets. Preference is given to using CO ₂ pellets whose size corresponds approximately to 5 to 15 times and in particular 10 times the mesh size. This has the advantage that the CO ₂ pellets remain on the sieve surface for a long time, thus ensuring efficient cooling through a longer sublimation time, and furthermore, the CO ₂ pellets can act as screening aids for a long time. With a Siebmaschenweite of about 1 mm, therefore, CO ₂ pellets are provided with a diameter of about 10 mm. For fine or Feinstabsiebungen correspondingly small CO ₂ pellets are provided which have a size of about 1 mm to 2 mm. For fine or fine screen sieving, the use of CO ₂ snow particles is also possible.

Preferably, a screening device is used, which has a cylindrical sieve, a vibrating, circular oscillating, tumbling or tumbling sieve.

When using the method according to the invention in a viewing device such. B. a classifier mill cools the cryogenic medium, for. As CO ₂ pellets, the good to be separated and acts as a separation aid, since it effectively prevents adhesion of the individual particles to each other and to the device.

The coldness of carbon dioxide ensures that many products that are sticky or lubricating at ambient temperature are no longer sticky at low temperatures. The use of CO ₂ pellets ensures a longer and thus more efficient cooling of the meal.

The method of the present invention is also suitable for use in centrifugal separators, gravity gauges, measuring cyclones, jet deflectors, air separators, planifiers and classifier mills.

As long as the CO ₂ pellets are significantly larger than the product to be separated, they will actively support the separation process by the sublimation cold and dead weight on cooling.

In accordance with a further aspect of the method according to the invention, the temperature in the sieve device or the sighting device can be set via a predetermined amount of cryogenic medium. Under flow rate is understood in the context of the present invention, a mass flow or a flow rate.

The invention will be explained in more detail below with reference to the drawings. These show in:

1 a Kaltmahlanlage with a sieve for spices in a schematic view,

2 a Kaltmahlanlage with a screening device for plastics in a schematic view, and

3 a Kaltmahlanlage with a viewing device in a schematic view.

A cold grinding plant 100 for spices ( 1 ) has a filler neck 1 for feeding the goods. In the filler neck, a mixer (not shown) is arranged to circulate the Guts. Below the filler neck 1 is a cellular wheel 2 arranged. The cell wheel 2 is via a feed line section 3 with a grinder 4 connected. The grinder 4 is as impact mill, z. B. formed as a pin mill. The grinder 4 is on a funnel-shaped collection container 5 arranged. Below the collection container 5 is a second cell wheel 6 intended. By means of the second cellular wheel 6 is the crushed Good or the intermediate product from the collection 5 dissipated.

Furthermore, the cold grinding plant has a cryogenic medium source 7 on. The cryogenic medium source in this embodiment is a liquid CO _{2 container} . The cryogenic medium source 7 is via a first connecting line section 8a with the feed line section 3 connected. In the connecting pipe section 8a is a feeder 9a such as a nozzle for generating CO ₂ snow or for supplying cold CO ₂ gas arranged.

The cryogenic medium source 7 For example, in an alternative embodiment, it may comprise a CO ₂ pellet reservoir filled with CO ₂ pellets at intervals. As CO ₂ pellets are here agglomerates of solid CO ₂ particles understood, the size and degree of compaction is selected as needed. The feeder 9a is then designed as a screw conveyor. It can also be a generating device 9a be provided to liquid CO ₂ from the medium source 7 Generate CO ₂ pellets or CO ₂ snow.

On the funnel-shaped collection container 5 is a filter 10 intended. The filter 10 is over a line section 11 with a fan 12 connected. The blower uses the mill gas for cleaning through the filter 10 aspirated. From the blower 12 leads a return line section 13 also in the feed line section 3 , From the return line section 13 branches a discharge line section 14 in which a throttle 21 is provided.

The grinder 4 additionally has liquid cooling. For this purpose, a cryo-tank 16 provided, via a cryogenic pipe 17 with the grinder 4 connected is. The cryo tank 16 contains a liquid coolant such as liquid CO ₂ , but it can also be other liquefied gases such. B. liquid nitrogen may be provided. The inflow of the liquid coolant is via a valve 18 controllable.

The collection container 5 after ordered second cellular wheel 6 opens into a connecting line section 22 leading to a screening device 23 leads. From the screening device 23 leads a discharge line section 24 path. The discharge line section is with a cellular wheel 31 connected to discharge the sifted Guts.

The cryogenic medium source 7 is via another connecting line section 8b with the sieve device 23 connected. In the second connecting line section 8b is a generation facility 9b intended. The generating device 9b is for producing CO ₂ pellets or CO ₂ snow from that from the cryogenic medium source 7 provided liquid CO _{2 is} formed. Such generating means are in the DE 10 2008 037 088 A1 , of the DE 10 2008 061 352 A1 and the not yet published DE 10 2009 057 265 A1 to which reference is hereby incorporated by reference.

The second connecting line section 8a flows into the screening device 23 above the in the sieve device 23 arranged sieves 30 , The screen mesh width of the screen 30 is between 0.01 mm and 10 mm.

Alternatively, a screw conveyor 9b Provided to the screening device on the line section 8b CO ₂ pellets from the CO ₂ pellet storage tank 7 supply. It can also be provided only a feeder to cool the material in the screening device directly with liquid CO ₂ from the medium source.

In the feed line sections 8a . 8b Controllers such as valves are provided to control the flow of liquid CO ₂ .

The sieve device 23 is over a line section 25 connected to the filler neck. About the pipe section 25 may be oversize from the screening device 23 be fed to the filler neck to grind it again and to use the residual cold of the oversize for cooling the goods.

In the event that the cryogenic medium source 7 and cryo-tank 16 both are designed to be used to supply cryogenic liquid CO ₂ , only a cryogenic medium source may be provided around the grinder 4 and the generator 9b to supply.

In the following, the method according to the invention will be described with reference to FIGS 1 illustrated Kaltmahlanlage 100 described.

About the filler neck 1 the material to be ground becomes the cellular wheel 2 fed. Good as spices, such. As pepper, nutmeg, allspice grains, etc., fabrics with fibrous grain shape, z. As tobacco dust, tea, leaf drugs or plastics, such. As polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), polypropylene (PP), polyamide, polyester, etc. provided. In the filler neck, the mixture is mixed with the mixer. About the cellular wheel 2 is the amount of good doses that the feed line section 3 and thus the grinder 4 is supplied.

While the estate is the feed line section 3 passes, becomes the good from the cryogenic medium source 7 over the connecting pipe section 8th and the feeder 9a cryogenic CO ₂ , for example, supplied CO ₂ snow.

Alternatively, the estate from the CO ₂ pellets reservoir 7 over the connecting pipe section 8th Supplied CO ₂ pellets in a suitable ratio.

The cold CO ₂ causes effective cooling of the Guts which embrittlement of the Guts is effected.

In this case, CO ₂ partially or completely sublimes after it has absorbed the heat of the material. The thereby forming gaseous phase of the carbon dioxide can from the feed line section 3 be deducted (not shown).

Subsequently, the good occurs alone or together with the remaining CO ₂ in the grinder 4 one. Due to the fact that the material now has a brittle condition, a lower grinding effort is required and a higher product throughput is achieved.

The estate falls from the grinder 4 in the funnel-shaped collection container 5 , Here, the still contained in the mixture CO ₂ gas through the filter 10 , the line section 11 , the blower 12 removed from the reservoir. Part of the container 5 extracted gas is via the return line section 13 returned to the device. About the discharge line section 14 that of the return line section 13 Discharges excess gas from the system 100 dissipated. The ratio between discharged and recycled CO ₂ gas is through the throttle 21 controlled. Part of the gas produced during the sublimation of the CO ₂ can also be used to cool the grinder 4 be used (not shown).

At the same time, the CO ₂ pellet production device 9b over the second connecting line section 8b liquid CO ₂ from the cryogenic medium source 7 fed. The CO ₂ pellet producer 9b leads the screening device 23 in a suitable ratio of CO ₂ pellets too. In the screening device 23 Cool the CO ₂ pellets the finely ground good. During the sieving process, the CO ₂ pellets roll on the goods and in this way support the sieving process by passing the material through the meshes of the sieve device 23 to happen evenly. This avoids that fine material or material shredded to the desired size, passes into the coarse material or insufficiently comminuted material and is discharged from the machine. In particular, an additional screening aid is dispensable in this way. In addition, it is effectively avoided that the fine-grained substrate is affected by air turbulence or by electrostatic charging.

About the discharge line section and the cellular wheel 31 the finely ground material is removed from the device. If necessary, oversize or coarse material can pass over the line section 25 to the filler neck 1 be returned to this again to grind and use the residual cold to cool the goods.

The in the screening device 23 sublimated CO ₂ gas may escape into the atmosphere or optionally be returned to the process as described for the mill gas. In another option, the CO ₂ gas remains as an inert gas in the fines stream.

In a further modification of this embodiment can also be provided, the CO ₂ pellets only the screening device 23 in order to utilize the cooling effect of the CO ₂ pellets on the finely ground material and to use the CO ₂ pellets as a screen aid when passing the material through the screening device.

In 2 is a cold grinding plant for thermoplastics 200 shown. It essentially corresponds to the one in 1 illustrated Kaltmahlanlage for spices 100 , However, in the supply line section is a cooling screw 19 arranged, dividing it into two subsections 3a . 3b shared. The connecting line section 8th flows into the cooling screw 19 , in turn, via the feed line section 3b with the grinder 4 connected is. The cryogenic medium source 7 is not with the cooling screw 19 connected. It is another cryogenic medium source 27 provided, via a line section 28 and a valve 18 with the cooling screw 19 connected. The cryogenic medium source 27 is z. B. formed for supplying cryogenic nitrogen. This can be done in the cooling screw 19 Good to be cooled with nitrogen before cold grinding. The sieve device 23 is via a connecting line section 26 with the filter 10 connected. In the connecting line section is a throttle valve 21 intended. Via the connecting line section 26 can exhaust gas from the screening device 23 the filter 10 be supplied.

The inventive method according to the second embodiment corresponds essentially to the basis of 1 described method.

It is understood that all options and modifications mentioned for the first embodiment are also applicable in the second embodiment.

A cold grinding plant 300 ( 3 ) has a reservoir 40 for feeding regrind. Below the storage tank 40 is a cellular wheel 41 arranged. The cell wheel 41 is via a feed line section 42 with a supply line 43 connected. It is a CO ₂ pellets storage tank 44 intended. Below the storage tank 44 is a cellular wheel 45 arranged. The cell wheel 45 is via a feed line section 46 with the supply line 43 connected. The feed line 43 flows into a classifier mill 47 ,

The classifier mill 47 has a housing 48 on. In the lower part of the case 48 is a facility for impact milling 49 arranged. The device for impact grinding 49 has rackets 50 on. By the thugs 50 The product is accelerated and when hitting in the housing 48 arranged grinding tracks (not shown) crushed. Above the egg direction for impact grinding 49 is a classifying wheel 51 arranged. About the classifying wheel 51 Fine particles are separated. These can be the classifying wheel 51 happen and are removed from the device.

The cold grinding plant 300 includes a blower 52 , The fan 52 generates an air flow, which is referred to below as transport gas. About a line section 53 is the fan 52 with the feed line section 43 and later on with the classifier mill 47 connected.

It is a cryogenic medium source 54 intended. The cryogenic medium source 54 is over a line section 55 in which a valve 18 is arranged with the line section 53 in the area of the classifier mill 47 connected.

The classifier mill 47 is with a discharge line section 56 Mistake. In the discharge line section 56 a temperature sensor (not shown) is arranged. Based on the temperature of the discharged Guts, the supply of cryogenic medium from the cryogenic medium source 54 and from the CO ₂ pellet reservoir 44 to be controlled.

The discharge line section 56 is with a centrifugal separator 57 connected. The centrifugal separator 57 or cyclone separator is designed for separating the goods from the transport gas. Below the centrifugal separator 57 is a cellular wheel 58 for discharging the goods from the cold grinding plant 300 arranged.

The centrifugal separator 57 is over a line section 59 with a filter device 60 connected. The filter device is over a line section 61 with the fan 52 connected. In the line section 61 is another line section 62 with throttle 21 intended.

In the following, the method according to the invention will be described with reference to FIGS 3 illustrated Kaltmahlanlage 300 described.

From the blower 52 a transport gas stream of air is generated. In the supply line 43 becomes the transport gas flow over the cellular wheel 41 Good to be ground from the reservoir 40 and over the cellular wheel 45 become CO ₂ pellets from the CO ₂ pellets reservoir 44 fed.

The CO ₂ pellets can either continuously in the container 44 be generated by means of generating CO ₂ pellets. It can also be provided the pellets automatically or manually the container 44 supply.

The transport gas stream with the material to be ground and the CO ₂ pellets enters the classifier mill. The classifier mill is over the line section 55 with cryogenic medium, e.g. As nitrogen or CO ₂ from the cryogenic medium source 54 applied to cool these. The CO ₂ pellets remain in suspension in the area of the classifying wheel 51 , They act as a release aid because they prevent adhesion of the fine particles to each other and to the Vorrrichtung.

By the thugs 50 the device for impact grinding 49 The material is accelerated and crushed when hitting the grinding paths (impact grinding).

Fine particles of the material pass through the classifying wheel 51 and are by means of the transport gas flow over the line section 56 from the classifier mill 47 dissipated. Coarse particles are thrown back into the area of the device for impact grinding or into the grinding chamber where they are further ground.

The milled material is fed to the centrifugal separator. Be in the centrifugal separator the particles of the goods have the desired size separated and on the feeder 58 removed from the device.

Air, exhaust and dust are passing over the pipe section 59 from the centrifugal separator 57 discharged and a filter device 60 fed. In the filter device, the dust is separated from the gaseous components. Residual cold gas contained is over the line section 61 the blower 52 supplied to use the residual cold. Excess gas from the device 300 is over the line section 62 and the throttle 21 removed from the device.

According to the exemplary embodiments, only a single cryogenic medium source can be provided in order to feed the grinder, the sieve device, the sighting device or other components of the device (eg, screw, 2 ) to cool.

In all embodiments of the present invention, the temperature inside the grinder or sifter may be adjusted by the amount of CO ₂ pellets supplied. Through the use of temperature sensors, the temperatures in the sifting device sieve device or the sighting device can be determined and adjusted precisely by means of the amount of CO ₂ pellets supplied.

LIST OF REFERENCE NUMBERS

1

filler pipe

2

feeder

3

supply conduit

3a, 3b

sections

4

grinder

5

Clippings

6

feeder

7

cryogenic medium source

8a, 8b

Connecting line sections

9a

feeding

9b

generator

10

filter

11

line section

12

fan

13

Return line section

14

Abführleitungsabschnitt

16

Cryogenic Tank

17

Trunking section

18

Valve

19

cooling screw

21

throttle

22

Trunking section

23

screening

24

Discharge line section

25

line section

26

line section

27

cryogenic medium source

28

line section

29

30

scree

31

feeder

40

reservoir

41

feeder

42

supply conduit

43

feed

44

CO ₂ pellet storage tank

45

feeder

46

supply conduit

47

OverviewAmenitiesPicture / Classifier

48

casing

49

Device for impact grinding / milling device

50

bat

51

classifying wheel

52

fan

53

line section

54

cryogenic medium source

55

line section

56

Abführleitungsabschnitt

57

cyclone

58

feeder

59

line section

60

filtering device

61

line section

100

Cold grinding plant (first embodiment)

200

Cold grinding plant (second embodiment)

300

Cold grinding plant (third embodiment)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4107872 A1 [0021]
• DE 102008037088 A1 [0052]
• DE 102008061352 A1 [0052]
• DE 102009057265 A1 [0052]

Claims (12)

A method of sifting or sifting, characterized in that a cryogenic medium is added to a material before or during sifting or sifting in order to cool the material. A method according to claim 1, characterized in that as a cryogenic medium nitrogen or carbon dioxide, in particular in the form of CO ₂ pellets or CO ₂ snow, is used. A method according to claim 2, characterized in that the CO ₂ pellets are added in an amount that they sieving the Guts through a sieve ( 30 ) by rolling on the screenings support. grinder A method according to claim 2 or 3, characterized in that the CO ₂ pellets in a screening device ( 5 ) and / or supplied in a visual device the estate. grinder A method according to claim 4, characterized in that the CO ₂ pellets are generated or stored directly on the screening device or the viewing device. Method according to claim 4 or 5, characterized in that CO ₂ pellets are used as sieving aid during sieving, which by rolling on the material thereof by meshing a sieve ( 30 ) of the screening device ( 5 ) happen. A method according to claim 6, characterized in that the size of the used CO ₂ pellets of 5 to 15 times the mesh size of the screen and in particular about 10 times the mesh size of the screen ( 30 ) corresponds. A method according to claim 4 or 5, characterized in that the temperature in a grinder of the screening device or the viewing device is adjustable via a predetermined Mengestrom on cryogenic medium. A method according to claim 7, characterized in that the sieve is a cylindrical sieve, a vibrating, Kreisschwing-, drum or a tumbling screen. Device for cooling goods during sieving or sifting, comprising a screening device or a viewing device and a cryogenic medium source ( 7 ), characterized in that the cryogenic medium source ( 7 ) is provided for providing cryogenic medium, wherein the sieve device ( 5 ) Milling device or the sighting device with the cryogenic medium source ( 7 ) are connected such that the Gutkryogenes medium before or at the screening or sifting is zusetzbar. Apparatus according to claim 10, characterized in that the cryogenic medium source ( 7 ) is provided for the provision of CO ₂ pellets, wherein the screening device ( 5 ) or the viewing device with the cryogenic medium source ( 7 ) are connected in such a way that CO ₂ pellets can be added to the material before or during sieving or sifting. Apparatus according to claim 10 or 11, characterized in that the sieve means a sieve ( 30 ) and the size of the used CO ₂ pellets of 5 to 15 times the sieve mesh of the sieve and in particular about 10 times the sieve mesh of the sieve ( 30 ) corresponds.

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