EP2722130A1 - Method and apparatus for creating dry ice snow, in particular for cleaning surfaces - Google Patents

Abstract

The method involves releasing partial conversion of the liquid carbon dioxide into a snow formation region (10) for cleaning the surfaces. The liquid carbon dioxide with the gas (G) is introduced into the snow formation region for producing dry ice snows. The produced dry ice snow is supplied through a specific channel (20) from a nozzle (30) connected with snow formation region and is delivered into the environment. The gas is introduced into snow formation region, in order to operate against the saturation with the carbon dioxide in snow formation region. An independent claim is included for device for generating dry ice snow package.

Description

The invention relates to a method and an apparatus for producing dry ice snow, in particular for cleaning surfaces.

Such methods and devices are used, among other things, for cleaning surfaces by accelerating the dry ice snow produced and directing it to the surface to be cleaned. It is known that the cleaning effect increases with the size of the dry ice particles or packages. Accordingly, an attempt is made to agglomerate the particles in snow-making chambers before they are introduced, for example, into a stream of compressed air, accelerated and shot through a nozzle onto a surface to be cleaned. On the other hand, it is known that the cleaning effect of such nozzles increases with the pressure of the accelerating carrier gas (eg compressed air). Often therefore pressures above the triple point pressure of CO ₂ (about 5.18 bar) are chosen.

According to the CO ₂ phase diagram is located at pressures above 5.18 bar, however, only solid CO ₂ from when the triple point temperature of CO ₂ falls below approximately -56.6 ° C. In the adiabatic expansion of liquid CO ₂ to pressures above 5.18 bar but this temperature is not exceeded. For example, it is just under -50 ° C for 7 bar, and still at -40 ° C for 10 bar. As a result, snowmaking chambers are ineffective at pressures above 5.18 bar.

On this basis, the object of the present invention is therefore to provide a method and an apparatus for producing dry ice snow which, even at pressures above the triple point pressure, permits comparatively simple production of dry ice snow.

This problem is solved by a method having the features of claim 1. Advantageous embodiments of the invention are specified, inter alia, in the subclaims.

According to claim 1, it is provided that in the method according to the invention for producing dry ice snow, liquid CO _{2 is} in particular adiabatically expanded into a snow-making area, wherein a gas is additionally introduced into the snow-making area to produce dry ice snow from the liquid CO ₂ introduced into the snow-making area, and wherein dry ice snow produced in the snow formation area is fed to a nozzle via a channel connected to the snow formation area and is emitted in particular jet-shaped into an environment via the nozzle.

The snow formation area can be e.g. be formed as a snowmaking chamber or as a snow formation pipe. Furthermore, the channel may be tubular.

Preferably, said gas is introduced into the snow formation area such that the gas phase in the snow formation area is not saturated with CO ₂ and therefore liquid CO _{2 introduced} into the snow formation area additionally at least partially evaporates in the snow formation area, thereby cooling and forming dry ice snow. In this case, the liquid CO ₂ is preferably expanded into the snow formation area in such a way that it forms a plurality of droplets, these cooling on partial evaporation and forming dry ice snow.

Preferably, it is provided in the method according to the invention that in the snow-forming area by introducing the additional gas, a supersaturation of the gas phase with carbon dioxide is achieved. This is preferably done at pressures above the triple point pressure of CO ₂ of 5.18 bar, more preferably at pressures between 6 bar and 12 bar.

Preferably, the liquid CO _{2 is} cooled on evaporation to a temperature less than or equal to the triple point temperature of CO ₂ (about - 56.6 ° C).

According to a variant of the method according to the invention, said gas additionally introduced into the snow formation area is air. However, other gases can also be introduced into the snow formation area in order to to prevent saturation of the gas phase in the snow formation area with CO ₂ and to achieve the cooling effect described above.

The dry ice snow thus produced in the snow formation area is supplied to the nozzle in an embodiment of the method according to the invention by means of a carrier gas introduced into the channel. The carrier gas is in particular air. Furthermore, the nozzle is preferably a Laval nozzle. In this case, in particular, the pressure prevailing in the channel is equal to the pressure prevailing in the snowmaking area or preferably corresponds at least approximately to the pressure prevailing in the snowmaking area. By means of the carrier gas and the nozzle, the generated dry ice snow is brought to a high speed and ejected into an environment. The dry ice snow jet thus produced may be e.g. To clean a surface to be directed to this.

In a variant of the method according to the invention it is provided that the snow formation area opens laterally into the channel, in particular so that a longitudinal axis of the snow formation area includes a non-vanishing, in particular acute angle with a longitudinal axis of the channel, in which - as described above - the carrier gas together with the dry ice snow is fed to the nozzle. In this case, the snow-forming area preferably opens into the channel upstream of that nozzle, wherein furthermore preferably the snow-forming area opens into the channel downstream of a carrier gas inlet of the channel through which that carrier gas is introduced into the channel.

As regards the introduction of the liquid CO ₂ into the snow-making area, in a variant of the method according to the invention, this is introduced or expanded into the snow-forming area in a first direction running parallel to the longitudinal axis of the snow-forming area.

The gas (eg compressed air) introduced to suppress the saturation of the gas phase with CO ₂ in the snowmaking area is preferably further introduced into the snowmaking area in a second direction, that second direction being parallel to a longitudinal axis of the snowmaking area or transverse to that longitudinal axis. When introduced transversely to the longitudinal axis, the gas in particular introduced tangentially to a circumferential direction of the snow formation area circumferential circumferential direction of the snow formation area in the snow formation area.

The introduction transversely to the longitudinal axis or the tangential introduction is preferred because the introduced gas and the introduced CO _{2 are} mixed more strongly by the swirl generated in this case. This promotes evaporation and increases the residence time in the snow formation area. The feed point or gas inlet of the snow formation area for the gas is preferably near an inlet of the snowmaking area, via which said liquid CO _{2 is introduced} into the snowmaking area, but may also extend along the longitudinal axis of the snowmaking area along the entire length of the snowmaking area up to the said one Channel are located.

In an alternative variant of the method according to the invention, provision is made for the snow formation area and that channel to be arranged coaxially with one another. In this case, it can be provided in a first embodiment of the method according to the invention that the channel surrounds the snow-forming area, so that the snow-forming area is at least partially arranged in the channel and thereby opens into the channel. The liquid CO ₂ or the gas can in this case be introduced into the snow-forming area according to one of the above-mentioned ways.

According to an alternative embodiment of the method according to the invention, provision can furthermore be made for the snow formation area to surround a section of the channel. Here, too, the liquid CO ₂ or the gas can be introduced into the snow-making area according to one of the above-mentioned methods, but preferably both the liquid CO ₂ and the gas in the first or second direction extending transversely to a longitudinal axis of the snow-forming area in the Snow formation are introduced, in particular each tangential to a circumferential axis of the snow formation area circumferential direction of the snow formation area (see above). This results in a better mixing of liquid CO ₂ and additionally introduced gas.

According to a further alternative embodiment of the method according to the invention, a plurality of snow-forming areas are provided, in particular at least two snow-forming regions, which are arranged at least in sections in the channel, wherein in each case the liquid CO ₂ and the gas are introduced separately into the individual snow-forming regions, so that in the individual snow-forming regions a saturation of the gas phase with CO _{2 is} counteracted (see above) and by cooling the liquid CO ₂ on evaporation of dry ice snow or dry ice snow packets are formed, which are in particular issued successively in the channel and are supplied by the carrier gas to the nozzle, which ejects the said packets.

This opens up the advantageous possibility of quasi-continuous loading of a surface with dry ice snow packages by successive individual pulses of dry ice packages.

The snow-forming areas can in turn be formed as snow-forming chambers or pipes.

According to a variant of this embodiment of the method according to the invention, it is provided that the gas is introduced into the respective snow formation area only until the respective snow formation area is filled with a predefinable amount of dry ice snow, in particular begins to clog, in the present case in particular being obstructed speaks if the cross section of the respective snow formation area perpendicular to the longitudinal axis of the respective snow formation area largely, in particular completely, is filled with dry ice snow. In order to promote clogging, the respective snow formation area may have a corresponding shape (e.g., tapering towards the channel). Furthermore, an inner side of the respective snow formation area, which comes into contact with the dry ice snow, have a surface structure conducive to the clogging.

After interrupting the supply of the gas into the respective snow-forming area, liquid CO ₂ is preferably further introduced into the respective snow-forming area, but due to the lack of additional gas or compressed air in the respective snow-making area, is no longer converted into solid CO ₂ or dry ice snow. but on the respective snow formation area or the respective snow formation area clogging dry ice snow, which in particular forms a "stopper" of solid CO ₂ in the respective snow formation area. That stopper or the dry ice snow in the respective snow formation area is preferably dissolved by liquid CO ₂ further introduced into the respective snow formation area, so that said dry ice snow leaves the respective snow formation area as a compacted dry ice snow package. Of course, the procedure described above can basically also be used if only a single snow-making area is present.

As experiments show, this phase transformation occurs very rapidly (in the range of about one second) in the snow formation area. Accordingly, in a series connection of e.g. Ten individual snow-making areas assume that about ten snow pulses per second are available for cleaning.

The adjustment of the flow of the gas into the respective snow formation area is preferably carried out via a respective valve associated with the respective snow formation area, in particular in the form of a solenoid valve. Furthermore, the said adjustment or metering of the gas can also take place via a distributor (for example in the form of a rotating perforated disc), which does not have to be absolutely gastight. Such a perforated disk is preferably configured in such a way that it releases only a part of the snow-forming regions for feeding in the gas, namely when, for example, a passage opening of the perforated disc comes to lie above the gas inlet of the respective snow formation area during rotation of the perforated disc.

It is also conceivable, instead of the gas, to introduce the liquid CO ₂ intermittently into the snow-forming areas. In this case, in particular, gas and liquid CO _{2 are introduced} into the respective snow formation area until a sufficient amount of dry ice snow, in particular the respective snow formation area, has formed. Then, the CO ₂ supply is interrupted (in particular analogous to the interruption of the air supply, see above), so that no further dry ice snow forms and the said, located in the respective snow formation area dry ice snow the respective Snow formation area by the pressure of the injected gas in the form of a compacted dry ice snow package leaves.

The interruption of the introduction of liquid CO ₂ or the introduction of the gas is preferably carried out cyclically for each snow formation area, so that the individual dry ice snow packages can be output one after the other from the snow-forming areas as described above, so that in particular a quasi-continuous blasting of the dry ice snow. Packages through the nozzle takes place.

In the event that a plurality of snow-forming regions are arranged in the channel, the liquid CO ₂ is preferably introduced into the respective snow-forming region in each case in a first direction running parallel to a longitudinal axis of the respective snow-forming region. Furthermore, that gas is preferably introduced in each case into the respective snow formation area in a second direction, wherein that second direction preferably runs parallel to a longitudinal axis of the respective snow formation area.

Furthermore, the problem according to the invention is solved by a device for producing dry ice snow having the features of claim 15, wherein that device is provided in particular for use or implementation of the method according to the invention.

According to claim 15, the device according to the invention comprises a snow formation area, a means for expanding liquid CO ₂ into the snow formation area for producing dry ice snow in the snow formation area, and a nozzle, in particular in the form of a Laval nozzle, for discharging the generated dry ice snow into an environment that nozzle is connected via a channel with the snow formation area. According to the invention, a means for applying the snow formation area with an additional gas is provided, in particular such that a saturation of the gas phase in the snow formation area with CO _{2 introduced is} counteracted. This is intended to ensure that liquid CO _{2 introduced} into the snow formation area at least partially evaporates in the snow formation area, thereby cooling and forming dry ice snow (see above). The snow-forming area may be formed as a snow-forming chamber or pipe, in particular at least partially hollow cylindrical. Likewise, the channel is preferably tubular, in particular at least partially hollow cylindrical, formed.

Said means is preferably designed to relax that liquid CO ₂ into the snow formation area, preferably adiabatically, in such a way that a multiplicity of CO ₂ droplets are formed, with the at least partial evaporation of those droplets continuing to cool them and forming dry ice snow. Said means for introducing liquid CO ₂ into the snow-forming area preferably comprises at least one CO ₂ source for providing liquid CO ₂ , eg in the form of a riser bottle, and preferably an inlet of the snow-forming area, eg in the form of a nozzle, through which that liquid CO ₂ in the snow formation area can be introduced, and further preferably a pipeline for connecting the CO ₂ source with said inlet. Preferably, said means further comprises a valve for throttling the introduction of liquid CO ₂ into the snow formation area.

Preferably, the means for applying the snow formation area with that gas is designed to introduce compressed air into the snow formation area as said gas. The means for impinging the snow formation area with said gas also preferably has a gas source for providing the gas (eg in the form of a gas cylinder or a compressor), and more particularly a gas inlet of the snow formation area for introducing the gas into the snow formation area, and further prefers a conduit for connecting the gas source to that gas inlet. The means for applying the snow formation area to that gas further preferably includes a valve for throttling the introduction of the gas into the snow formation area.

According to a further embodiment of the device according to the invention, this has a means for introducing a carrier gas into the channel, so that it entrains the dry ice snow produced in the snow formation area and supplies it to the nozzle.

Preferably, the means for introducing the carrier gas into the channel comprises a carrier gas source for providing the carrier gas (eg in the form of a carrier gas source) Compressor), and more particularly, a carrier gas inlet of the snow formation area for introducing the carrier gas into the snow formation area, and further preferably a pipe for connecting the gas source to that carrier gas inlet. The means for introducing the carrier gas into the channel preferably further comprises a valve for throttling the introduction of the carrier gas into the snow formation area. The carrier gas is preferably air. If air as said gas is also introduced into the snow-making area, it may be possible to use a common gas or air source.

According to a variant of the device according to the invention, it is provided that the snow-forming area opens laterally into the channel, in particular such that a longitudinal axis of the snow-forming area forms a non-disappearing, in particular acute angle with a longitudinal axis of the channel, wherein in particular the snow-forming area opens into the channel upstream of that nozzle and in particular wherein the snow formation area downstream of a carrier gas inlet of the channel, through which that carrier gas is introduced into the channel, opens into the channel.

According to a further embodiment of the device according to the invention, it is provided that the snow formation area and that channel are arranged coaxially with one another. In this case, either that channel can surround the snow formation area or the snow formation area can at least partially surround the channel (see above).

Furthermore, as already described above, the device according to the invention or the means for introducing liquid CO ₂ into the snow formation area is preferably designed to introduce or to relax the liquid CO ₂ in a first direction into the snow formation area which is parallel to a longitudinal axis the snow formation area extends or transverse to that longitudinal axis.

Furthermore, as already described above, the device according to the invention or the means for acting on the snow formation region with said gas is preferably designed to introduce that gas into the snow formation region in a second direction, that second direction being parallel to a longitudinal axis of the snow formation region transverse to that longitudinal axis According to a further embodiment of the device according to the invention, it is provided that it has a plurality, but at least two, of snow-forming regions connected to the channel (eg in the form of snow-forming chambers or tubes), which are arranged at least in sections in the channel. The means for introducing liquid CO ₂ is then preferably designed in accordance to initiate in the snow forming regions liquid CO ₂ and preferably for each snow formation region adjustable separately. Likewise preferred is that means for acting on the snow formation area with said gas to pressurize the individual snow formation areas with the gas, wherein preferably in turn the loading of the individual snow formation areas with the gas for each snow formation area is separately controllable.

The two said means are preferably designed to charge the snow-forming regions with liquid CO ₂ and the gas in such a way that dry ice snow packages are formed in the individual snow-forming regions, which are ejected, in particular, successively into the channel, in particular the liquid CO _{2 in} each case is introduced into the respective snow formation area in a first direction running parallel to a longitudinal axis of the respective snow formation area, and wherein in particular that gas is introduced into the respective snow formation area in a second direction, that second direction being parallel to a longitudinal axis of the respective snow formation area.

Furthermore, the means for introducing CO ₂ can be designed to throttle or interrupt the introduction of the liquid CO ₂ in particular cyclically for interrupting a dry ice snow formation in the respective snow formation area. Alternatively, the means for acting on the snow formation area with the gas may be designed to cyclically throttle or interrupt the admission of the respective snow formation area to the gas for interrupting dry ice snow formation in the respective snow formation area (see above).

As a result, the method according to the invention and the device according to the invention make better cleaning possible, especially at pressures above 5.18 bar. In addition, the coaxial arrangements of the snow formation area or of the channel compared with the nozzles used today have the advantage that they do not tend to unsteady behavior or "spitting" of the nozzle. The latter happens especially with asymmetrically constructed nozzles, where agglomerated particles collect, especially in the transition region between the channel and the snow formation area, and dissolve from time to time, whereby the cleaning effect becomes uneven.

Further details and advantages of the invention will be explained by the following description of exemplary embodiments with reference to the figures.

Fig. 1

eine schematische Schnittansicht einer erfindungsgemäßen Vorrichtung zur Erzeugung von Trockeneisschnee mit einer schräg in den Kanal der Vorrichtung einmündenden Schneebildungsbereich;

Fig. 2

eine schematische Schnittansicht entlang der Linie II-II der Figur 1;

Fig. 3

eine schematische Schnittansicht einer Abwandlung der in der Figur 1 gezeigten Vorrichtung, bei der der Schneebildungsbereich und der Kanal koaxial zueinander angeordnet sind, wobei der Kanal den Schneebildungsbereich umgibt;

Fig. 4

eine schematische Schnittansicht einer Abwandlung der in der Figur 3 gezeigten Vorrichtung, wobei der Schneebildungsbereich den Kanal umgibt;

Fig. 5

eine schematische Schnittansicht einer Abwandlung der in der Figur 4 gezeigten Vorrichtung;

Fig. 6

eine schematische Schnittansicht entlang der Linie VI-VI der Figur 5

Fig. 7

eine schematische Schnittansicht einer erfindungsgemäße Vorrichtung mit mehreren Schneebildungsbereichen;

Fig. 8

eine schematische Schnittansicht entlang der Linie VIII-VIII der Figur 7; und

Fig. 9

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung mit Mitteln zum Einleiten von flüssigem CO₂, Gas bzw. Trägergas in die Vorrichtung.

Show it:

Fig. 1

a schematic sectional view of an apparatus according to the invention for the production of dry ice snow with an obliquely opening into the channel of the device snow formation area;

Fig. 2

a schematic sectional view taken along the line II-II of FIG. 1 ;

Fig. 3

a schematic sectional view of a modification of the in the FIG. 1 in which the snow formation area and the channel are arranged coaxially with each other, the channel surrounding the snow formation area;

Fig. 4

a schematic sectional view of a modification of the in the FIG. 3 apparatus shown, wherein the snow formation area surrounds the channel;

Fig. 5

a schematic sectional view of a modification of the in the FIG. 4 shown device;

Fig. 6

a schematic sectional view taken along the line VI-VI of FIG. 5

Fig. 7

a schematic sectional view of an apparatus according to the invention with several snow forming areas;

Fig. 8

a schematic sectional view taken along the line VIII-VIII of FIG. 7 ; and

Fig. 9

a schematic representation of a device according to the invention with means for introducing liquid CO ₂ , gas or carrier gas into the device.

FIG. 1 shows an inventive device 1 for producing dry ice snow with a snow formation area 10. In experiments with such devices 1 has been shown that even at pressures above the triple point pressure of CO ₂ of about 5.18 bar dry ice snow is generated in the snow formation area 10, when There additionally controlled a gas G such as compressed air is introduced. As a result, 10 temperatures below the triple point temperature of CO ₂ of about -56.6 ° C can be achieved in the snow formation area.

For this purpose, liquid CO ₂ is preferably expanded into the snow formation area 10, a mixture of liquid and gaseous CO _{2 being formed} in the snow formation area 10. The ratio of liquid CO ₂ to gaseous CO ₂ is dependent on the pressure and the temperature of the CO ₂ . The admixture of the other gas G now leads to the fact that the gas phase in the snow formation area 10 is not saturated with CO ₂ . Additional CO ₂ therefore evaporates from the liquid CO ₂ droplets in the snow formation area 10 to saturate the gas phase with CO ₂ . In this case, the respective droplet continues to cool and falls below the triple point temperature (about -56.6 ° C), so that solid CO ₂ forms as a result.

The interference of said gas G in the snow formation area 10 can, for example, according to the in the FIGS. 1 to 8 shown variants are made.

According to FIG. 1 For example, the apparatus 1 has a snow formation area 10 extending along a longitudinal axis L in the form of a snow formation pipe 10, into which liquid CO ₂ is introduced via an inlet 21 into the snow formation area 10 along a first direction R which is oriented parallel to the longitudinal axis L. The additionally introduced into the snow making area gas G, which is, for example, compressed air is introduced along a second direction R 'in the snow formation area 10, either axially parallel to the liquid CO ₂ or alternatively transverse to the longitudinal axis L of the snow formation area, as in FIG. 2 is indicated. In this case, the introduction of the gas G is tangential to a circumferential direction U of the snow formation area 10. The tangential introduction is to be favored, since the gas G and the CO _{2 are} more strongly mixed by the swirl generated. This promotes evaporation and increases the residence time in the snow formation tube 10. The feed point is preferably close to the carbon dioxide feed, ie, adjacent to the inlet 21, but may extend along the entire length of the snow formation area 10 to a channel 20 (also referred to as a compressed air channel). are located, in which the snow formation area 10 opens. The channel 20 extends along a longitudinal axis L ', which preferably encloses an acute angle W with the longitudinal axis L of the snow formation region 10. A carrier gas T, in particular in the form of compressed air, is fed into the channel 20 upstream of the confluence of the snow formation area 10 via a carrier gas inlet 23 which is at approximately the same pressure level as the snow formation area 10. The carrier gas T generates the carrier gas in the snow formation tube 10 Dry ice snow is entrained to a nozzle 30 (eg, in the form of a Laval nozzle) formed at an end portion of the channel 20 through which the dry ice snow is ejected from the apparatus 1, for example, to impinge a surface for cleaning purposes.

According to FIG. 3 is the snow formation area 10 or the snow formation tube 10 in contrast to FIG. 1 arranged coaxially with the channel 20, so that the two longitudinal axes L, L 'coincide, wherein the snow formation area 10 is surrounded by the channel 20 so that it forms a ring tube in this area. The feed of liquid CO ₂ and the gas G (eg pressure gap) can be analogous to the Figures 1 and 2 be made.

FIG. 4 represents a modification of the variant according to FIG. 3 wherein now the snow formation area 10 is formed as a ring tube and an end portion of the channel 20 at which the carrier gas inlet 23 is provided encloses, for example, the liquid CO ₂ via the ring tube 10 provided on the inlet 21 along a parallel to the longitudinal axis L of the ring tube 10 extended first direction R in the snow formation area 10 and the annular tube 10 can be fed, wherein preferably the gas G transversely to the longitudinal axis L of the annular tube 10 introduced into this to improve mixing with CO ₂ (see above). The introduction preferably takes place tangentially to the circumferential direction U of the snow formation region 10 or of the annular tube 10, as in FIG FIG. 6 indicated.

According to FIG. 5 Furthermore, the liquid CO ₂ , as in FIG. 6 shown, transversely to the longitudinal axis L of the annular tube 10 are entered into this, the introduction preferably - as described above - is tangential. This has opposite to the variant according to FIG. 4 the advantage that the mixing of CO ₂ and gas G can be further improved.

Furthermore, according to FIG. 7 a plurality of snow-forming regions 10 may be provided in the form of the snow-making tubes 10, which are each at least partially arranged in the end portion of the channel 10, wherein those snow-forming tubes 10 are preferably arranged parallel to each other along a circumferential direction of the channel 20, in particular equidistantly from each other, as in FIG. 8 is shown. The longitudinal axes L of the individual snow formation tubes 10 run parallel to the longitudinal axis L 'of the channel 20.

Thus, in place of the annular tube 10 according to FIGS. 4 and 5 individual snow-making tubes 10. The snow-making tubes 10 can be charged independently of each other with CO ₂ and the gas G. This opens up the possibility of performing an almost continuous cleaning by individual pulses of dry ice packets. In this case, the gas G or the compressed air G is not continuously, but only as long introduced into the respective snow formation area 10 until it begins to clog. This behavior can be promoted by a corresponding shape or surface of an inner side 10 a of the respective snow formation area 10. Thus, the snow forming tubes 10 may be tapered towards the channel 20 or have flow resistances (eg constrictions). Furthermore, the said inner sides 10a may have a certain roughness.

After switching off the supply of the gas G liquid CO ₂ continues to flow into the respective snow formation tube 10, which is no longer converted into solid CO ₂ for lack of the gas G or the compressed air G. It hits the "plug" of solid CO ₂ , dissolves it after a short time, so that this leaves the nozzle 30 as a compacted dry ice pack.

The metering of the gas G to the individual snow making tubes 10 may be carried out according to FIG. 9 eg via individual valves 53, in particular solenoid valves, take place, wherein FIG. 9 only such a valve 53 shows by way of example. Alternatively, a simple distributor (eg a rotating perforated disc) is conceivable which does not have to be absolutely gas-tight and, for example, could be integrated into a device 1 in the form of a cleaning pistol. It is advisable to drive such a perforated disc over one of the already existing gases.

It is also conceivable, instead of the gas G, to introduce the liquid CO ₂ intermittently into the snow-forming regions 10. As a result, compacted dry ice snow packets can also be generated and output from the device 1 one after the other.

As in FIG. 9 are shown for introducing the liquid CO ₂ and the gas G and the carrier gas T in the one or more snow forming areas or in the channel 20 preferably corresponding means 40, 50, 60 are provided.

Such means 40 for introducing CO ₂ into one or more snow-forming regions 10, as for example in the FIGS. 1 to 8 For example, there is a CO ₂ source 41, for example in the form of a riser bottle 41, which is connected via a pipeline 42 and a valve 43 to the inlet 21 of a cryogenic formation region 10. If several snow forming areas 10 are present (cf., for example FIG. 8 ), so preferably a corresponding plurality of valves 43 are provided, so that the supply of CO ₂ for each chamber 10 can be controlled individually. The same applies to the means 50 for applying the snow formation region (s) to the said gas G. Here too, the said means 50 preferably has a gas source 51 for providing the gas G, which is, for example, a gas bottle 51 or a compressor can act. The gas source 51 is preferably connected via a pipeline 52 to the gas inlet 22 of the respective snow formation area 10. Here, too, a metering of the gas G into the respective snow formation area 10 can take place via a valve 53. In several snow-making chambers 10 a plurality of valves 53 are correspondingly present.

Finally, the means 60 for introducing the carrier gas T into the channel 20 also has a carrier gas source 61 (eg in the form of a compressor) which provides the carrier gas T (eg compressed air). The carrier gas source 61 is also preferably connected via a conduit 62 to the carrier gas inlet 23 of the channel 20. Via a corresponding valve 63, the supply of carrier gas T in the channel 20 can be controlled.

LIST OF REFERENCE NUMBERS

1 Device for producing dry ice snow 10 Snow-forming region 10a inside 20 channel 21 inlet 22 gas inlet 23 Carrier gas inlet 30 jet 40 Means for introducing liquid CO 2 into the snow formation area 41 CO ₂ source 42 pipeline 43 Valve 50 Means for applying the snow formation area with gas (e.g., compressed air) 51 Gas source 52 pipeline 53 Valve 60 Means for introducing carrier gas into the channel 61 Carrier gas source 62 pipeline 63 Valve G Gas (eg compressed air) T Carrier gas (e.g., compressed air) L, L ' longitudinal axis W angle R First direction R ' Second direction U circumferentially

Claims (13)

Process for the production of dry ice snow, in particular for cleaning surfaces, in which liquid CO _{2 is expanded} with partial conversion into gaseous CO ₂ into a snow formation area (10), wherein for the production of dry ice snow from the liquid CO ₂ introduced into the snow formation area (10) additionally a gas (G) is introduced into the snow formation area (10), and wherein dry ice snow produced in the snow formation area (10) is fed to a nozzle (30) via a channel (20) connected to the snow formation area (10) and via the nozzle (10). 30) is discharged into an environment. A method according to claim 1, characterized in that that gas (G) is introduced into the snow formation area (10) to counteract saturation of the gas phase with CO ₂ in the snow formation area (10) so that liquid CO introduced into the snow formation area (10) ₂ evaporates in the snow forming area (10), thereby cooling and forming dry ice snow. A method according to claim 1 or 2, characterized in that the snow formation area (10) is under a pressure which is in particular greater than or equal to the triple point pressure of CO ₂ . The method of claim 2 or claim 3 when dependent on claim 2, characterized in that that liquid CO ₂ is less than or equal to the triple point temperature of CO ₂ is cooled to a temperature during evaporation. Method according to one of the preceding claims, characterized in that the additionally introduced into the snow formation area (10) gas (G) is air. Method according to one of the preceding claims, characterized in that the dry ice snow produced by means of a channel (20) introduced carrier gas (T) of the nozzle (30) is fed, wherein the carrier gas (T) is in particular air. Method according to one of the preceding claims, characterized in that the snow formation area (10) opens laterally into the channel (20), in particular so that a longitudinal axis (L) of the snow formation area (10) has a non-vanishing, in particular acute angle (W) In particular, the snow formation region (10) opens into the channel (20) upstream of that nozzle (30), and in particular the snow formation region (10) downstream of a carrier gas inlet (23) of the channel (20). 20), through which that carrier gas (T) is introduced into the channel (20), opens into the channel (20). Method according to one of claims 1 to 6, characterized in that the snow formation area (10) and the channel (20) are arranged coaxially with each other. Method according to one of the preceding claims, characterized in that the liquid CO ₂ in a first direction (R) in the snow formation area (10) is initiated, wherein said first direction (R) parallel to a longitudinal axis (L) of the snow formation area (10) runs or transverse to that longitudinal axis (L). Method according to one of the preceding claims, characterized in that the gas (G) in a second direction (R ') in the snow formation area (10) is initiated, wherein said second direction (R') parallel to a longitudinal axis (L) of the snow formation area (10) runs or transverse to that longitudinal axis (L). Method according to one of Claims 1 to 6, characterized in that the liquid CO ₂ and the gas (G) are introduced into a plurality of snow formation regions (10) connected to the channel (20), which are at least partially introduced into the channel (20). In particular, the snow-forming regions (10) are charged with liquid CO ₂ and the gas (G) in such a way that dry ice snow packages are formed in the individual snow-forming regions (10), which in particular successively enter the channel (20). In particular, the liquid CO _{2 in} each case in a parallel to a longitudinal axis (L) of the respective snow formation region (10) extending first direction (R) is introduced into the respective snow formation area (10), and wherein in particular that gas (G) respectively in a second direction (R ') is introduced into the respective snow formation area (10), wherein said second direction (R') is parallel to a longitudinal axis (L) of the respective snow formation area (10). A method according to claim 11, characterized in that for interrupting a dry ice snow formation in the respective snow formation area (10), the introduction of the liquid CO ₂ or that gas (G) is throttled and / or interrupted. Device for producing dry ice snow, in particular for applying a surface with dry ice snow, with: a snow formation area (10), a means (40) for releasing liquid CO ₂ into the snow formation area (10) for producing dry ice snow in the snow formation area (10), and a nozzle (30) for discharging the dry ice snow into an environment, the nozzle (30) being connected to the snow formation area (10) via a channel (20),
marked by
a means (50) for acting on the snow formation area (10) with an additional gas (G), in particular such that saturation of the gas phase in the snow formation area (10) with CO _{2 introduced is} counteracted.

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