EP2658678A1

EP2658678A1 - Device and method for particle blasting with frozen gas particles

Info

Publication number: EP2658678A1
Application number: EP11773703.1A
Authority: EP
Inventors: Robert Veit
Original assignee: Ipal Gesellschaft fur Patentverwertung Berlin Mbh
Current assignee: Ipal Gesellschaft fur Patentverwertung Berlin Mbh
Priority date: 2010-12-30
Filing date: 2011-10-07
Publication date: 2013-11-06
Also published as: WO2012089359A1; DE102010064406A1

Abstract

The invention relates to a method for generating a mixed jet including frozen particles, in particular CO2 particles and a carrier gas comprising the steps: introducing a liquefied gas into an expansion cavity for generating a flow of agglomerated frozen particles from the liquefied gas; supplying the flow of agglomerated particles and a carrier gas flow to an acceleration nozzle for generating and accelerating a mixed gas jet including the frozen particles and the carrier gas. The following method alternatives are proposed to prevent particle agglomerations: lowering the pressure dew point, heating a wall of the expansion cavity and/or of the acceleration nozzle and/or introducing an additional gas flow in the form of an additional gas for increasing and/or controlling the flow velocity in the interior of the expansion cavity.

Description

Device and Method for Particle Blasting with Frozen Gas Particles

The invention relates to a device and a method for pressure blasting with a mixed jet, including frozen gas particles and a carrier gas. In particular, the invention relates to a device and a method for C0₂ snow blasting through a mixed jet including frozen C0₂ gas particles and a carrier gas. Frozen gas particles are particles of a material which is gaseous for a normal ambient temperature and a normal ambient condition.

Blasting with solid carbon dioxide became popular in recent years for various applications. As soon as sensitive surfaces have to be unlayered or cleaned or a secondary contamination with blasting media is undesirable, this technology can bring its advantag- es to bear.

The low hardness of solid carbon dioxide facilitates processing a large variety of materials without damage. Furthermore, since the blasting media sublimates only the removed pure single material, coating or contamination has to be disposed of.

When blasting with frozen gas particles, the blasting medium is pneumatically accelerated and applied to the surface to be processed. Contrary to a purely mechanical effect of other blasting media, blasting with frozen gas particles is based on three different operating mechanisms. The low temperature of the blasting medium causes thermal stress between coating and contamination of the substrate. Furthermore, the kinetic energy of the frozen gas particles leads to a mechanical separation which is supported through the third effect, the pressure surge, due to the sudden sublimation of the frozen gas particles.

Devices and methods for frozen C0₂ blasting are known in principle, and there is a plural- ity of different configurations which give the mixed jet, including frozen gas particles and the carrier gas, different properties with respect to speed, volume flow, size, number and configuration of the frozen gas particles so that a desirable effect on the work piece or the surface can be achieved during operations.

Thus, a differentiation is made in particular between two different basic configurations. The first configuration, which is also designated as dry ice blaster, differs from the second configuration, which is also designated as snow blaster, in that the first generates the mixed jet from the solid phase and the second generates the mixed jet from the liquid phase. For dry ice blasting, the blasting medium is produced in a separate process in the form of pellets or blocks and subsequently added to the compressed airflow in a blasting unit.

Since it is an object of the present invention to provide a device for pressure blasting with frozen gas particles wherein the device is small in size and can thus be integrated easily into machinery and equipment, the present invention relates to a device for pressure blasting through a mixed jet made from frozen gas particles and a carrier gas according to the second configuration. Accordingly, in the devices described herein, the blasting medium, in particular C0₂, is stored under pressure in a liquid form.

Also in this configuration, designated as a snow blaster, there are two different configuration variants: A two-substance ring nozzle and a jet nozzle with an agglomeration chamber. In the two-substance ring nozzle, the liquid gas is expanded at the jet exhaust to ambient pressure. The snow particles that are being generated are bundled and accelerated through an enveloping jet made from supersonic compressed air.

The frozen gas particles formed in the two-substance ring nozzle have a smaller diameter compared to the jet nozzle with the agglomeration chamber and, thus, have lower kinetic energy at the same velocity. Therefore, the particles which are generated with this confi- guration are not very abrasive, and devices of this type are typically used for cleaning components with fine surface structures that are highly sensitive. A device of this type is described in DE 199 26 1 19 C2.

In a device of the second configuration type, the liquefied gas is introduced into an ag- glomeration chamber together with the carrier gas flow and expanded. Compared to the two-substance ring nozzle, larger snow particles are provided which are accelerated through the compressed air in a subsequent nozzle and provide a significantly higher abrasive effect. A method and a device of this type are described in DE 102 43 493 B3.

While the first configuration variant with dual substance nozzle has the disadvantage that it has low abrasiveness, the second configuration variant of the pressure blasting device with agglomeration chamber has the disadvantage that a high pressure use is provided during operations. Furthermore, frozen gas particles accumulate in the interior of the agglomeration chamber at the outer walls and separate at infrequent time intervals and with undefined sizes from the exterior walls. This provides pulsating at higher removal performances and, thus, an inhomogeneous blasting pattern.

From DE 202 14 063 U1 , a C0₂ cold gas jet is known for pressure blasting through a mixed jet made from C0₂ particles and compressed air. Thus, a dense fluid is introduced through an inner tube which is enveloped by a gas conduit. The flows of the gas and of the dense fluid join in a nozzle that converges in blasting direction. Thus, the inner tube is configured so that its end oriented away from the inlet can be pulled back into a chamber which has a larger cross-section compared to the constant cross-section of the inner tube.

Document US 5,725, 154 shows a spray gun for cleaning, using a dense fluid like C0₂. Thus, a dense fluid is introduced through an inner tube which is enveloped by a gas conduit. In a nozzle that converges in jet direction, the flows of the gas and of the dense fluid join. Thus, the inner tube is configured so that its end oriented away from the inlet can be pulled back into a chamber which has greater cross-section compared to the constant cross-section of the inner tube.

From DE 10 2007 018 338 A1 , a device for particle blasting with frozen particles is known which stores the blasting medium in liquid form and, thus, is among the group of the snow blasters. The device includes a nozzle housing which includes an outer and an inner cavity. Thus, the inner cavity represents an expansion or agglomeration cavity which includes an inlet connected with the liquefied gas supply for introducing a liquefied gas at its upstream longitudinal end and a nozzle opening at its downstream longitudinal end. Thus, the nozzle opening includes a substantially greater cross-section than the inlet. This inner cavity is enveloped by an outer cavity at least in the portion of the outlet opening of the inner cavity, wherein the outer cavity is connected with at least one carrier gas supply. After the outlet opening of the expansion cavity and after the outer cavity an initially converging acceleration nozzle is connected in flow-direction wherein the acceleration nozzle includes a carrier gas inlet arranged laterally, preferably on all sides of the outlet opening, wherein the carrier gas outlet is configured as an outlet of the outer cavity. The cross-section of the carrier gas outlet is variably adjustable.

During the flow of the mix of frozen gas particles and gas through the expansion cavity, the particular particles agglomerate with one another so that an enlargement of the particles occurs downstream in the expansion or also agglomeration cavity. The diameter of the expansion cavity is configured so that the cross-section of the expansion cavity continuously expands downstream. This cross-section expansion of the expansion cavity towards the nozzle exhaust provides a continuous flow and, thus, a safe transportation of the snow particles created. For a constant cross-section, an agglomeration and accumulation of solid gas particles occurs in the fluid dynamic "dead spaces" directly after intro- ducing the liquefied gas through jets. These agglomerations come loose in infrequent intervals so that an inhomogeneous and pulsating jet pattern of the nozzle is provided which is known in the art as "coughing." The comparatively large particle agglomerations have a higher kinetic energy and, thus, impact the blasted surface more strongly. This effect is detrimental for a reproducible application of snow blasting technology. Further- more, the agglomeration of frozen gas particles can lead to a plugging of the jet nozzle.

The inventors have found that undesirable agglomerations can still occur in spite of the described known configuration.

Thus, it is a goal of the present invention to provide a mixture blasting technology which further reduces the problem of possible agglomerations. In order to achieve the object, the following solutions are proposed: Reducing the pressure dew point of the carrier gas; heating the carrier gas; providing a low-adhesion inner wall of the expansion cavity; providing a low-adhesion outer wall of the expansion cavity; - providing a low-adhesion inner wall of the acceleration nozzle; controlled heating of the walls of the expansion cavity, e.g. through integrated resistance heating wires; controlled heating of the wall of the acceleration nozzle, e.g. through integrated resistance heating wires; - introducing an additional gas for increasing or controlling the flow velocity in the interior of the expansion cavity. For this purpose, gaseous C0₂ may be used, which is taken from the same storage container as the C0₂ for generating the snow particles. This additional gas flow can also be used for flushing the expansion cavity after turning off the nozzle. Thus, the switching properties of the unit can be improved.

The solutions can be implemented alternatively or in a cumulative manner.

In a method for generating a mixed jet including frozen particles, in particular C0₂ particles and a carrier gas the goal can be achieved with the method steps:

Introducing a liquefied gas into an expansion cavity for generating a flow of agglomerated frozen particles from the liquefied gas and supplying the flow of agglomerated particles and a carrier gas flow to an acceleration nozzle for generating and accelerating a mixed gas jet including the frozen particles and the carrier gas.

The following method alternatives are proposed accordingly for achieving the object: Lowering the pressure dew point, so that there are no particle agglomerations in the expansion cavity and/or the acceleration nozzle; heating a wall of the expansion cavity and/or of the acceleration nozzle and/or introducing an additional gas flow in the form of an additional gas for increasing and/or controlling the flow velocity in the interior of the expansion cavity.

In the latter case, the liquefied gas is preferably C0_2, and gaseous C0₂ is preferably used for an additional gas for increasing and/or controlling the flow velocity in the interior of the expansion cavity.

According to another preferred variant of the latter method, the additional gas flow is used for flushing the expansion cavity after the nozzle is turned off.

In all method variants, the carrier gas is preferably heated.

For a device for pressure blasting through a mixed jet made from particles of a frozen gas and a carrier gas with an expansion cavity, which includes an inlet for introducing a liquefied gas into the expansion cavity at its longitudinal upstream end and an outlet opening at its downstream longitudinal end, wherein the outlet opening has a much larger cross-section than the inlet opening, at least one liquid gas supply which is connected with the inlet of the expansion cavity, - a carrier gas supply, and an acceleration nozzle which connects to the outlet opening of the expansion cavity downstream and initially converges in flow-direction, and which is connected with the acceleration nozzle of the expansion cavity and the carrier gas supply, the following embodiments are feasible which can be implemented alternatively or cumulatively:

A wall of the expansion cavity and/or a wall of the acceleration nozzle are provided with an anti-adhesion coating; - a wall of the expansion cavity and/or a wall of the acceleration nozzle are provided with a heater for heating the wall; the device includes means for adjusting and/or lowering a pressure dew point of the carrier gas and/or the device includes an additional gas supply which leads into the expansion cavity in order to be able to provide an additional gas to the expansion cavity during operations for increasing or controlling the flow velocity in the interior of the expansion cavity.

A suitable and, therefore, preferred means for adjusting and/or lowering a pressure dew point of the carrier gas is a carrier gas heater. Preferred variants of all devices are cha- racterized by the following features:

A nozzle housing, which encloses an outer cavity and an inner cavity, wherein the inner cavity forms the expansion cavity, and wherein the outer cavity envelops the inner cavity at least partially in the portion of the outlet opening, - wherein the carrier gas supply is connected with the outer cavity, and wherein the acceleration nozzle includes a carrier gas outlet for an outlet of the outer cavity that is arranged laterally with respect to the outlet opening, wherein the cross-section of the outlet is variably adjustable. The carrier gas inlet is preferably arranged in an annular manner between the outlet opening of the expansion cavity and a wall of the acceleration nozzle that converges in flow direction.

Further preferred features of the device are:

A tube-like wall, separating the inner cavity from the outer cavity if made from plastic material, having anti-adhesive properties, is provided; a nozzle portion of the device that includes the acceleration nozzle is interchangeable; the outer cavity is enclosed by an outer tube that holds the acceleration nozzle and is movable relative to a tube-like wall separating the inner cavity and the outer cavity from each other. Preferably, the outer tube is connected via a helical joint to the tube-like wall so that a ration of the outer tube translates into an axial relative movement of the outer tube and the acceleration nozzle relative to the tube-like wall; the outer tube encloses an insulation layer made from non-adhesive plastic material.

Additional features and advantages of the present invention are subsequently described with reference to the appended drawing Figure, wherein

FIG. 1 illustrates a known snow blasting nozzle in a cross-sectional view;

FIG. 2 illustrates where undesirable agglomerations can occur in the device according to FIG. 1 ;

FIG. 3: is a perspective view of a preferred embodiment of a snow blasting nozzle according to the invention;

FIG. 4: is a cross-sectional view of the preferred embodiment of a snow blasting nozzle according to the invention. The device illustrated in FIG. 1 for pressure blasting includes a nozzle housing 4 which includes an outer cavity 6 (or outer chamber 6) and an inner cavity 2 (or inner chamber 2). The inner cavity 2 and the outer cavity 6 are separated from each other by means of a tube-like wall 1 1 . The inner cavity 2 is connected with a supply 7 for introducing liquefied gas into the inner cavity 2. The outer cavity 6 in turn is connected with a supply 3 for introducing pressurized carrier gas into the outer cavity 6.

The inner cavity 2 is defined at one of its longitudinal ends by an inlet 8 which is provided according to the illustrated embodiment through the inner diameter of a dosing device 1 . The dosing device 1 is arranged in a transition portion between the supply 7 and the inner cavity 2. The dosing device 1 in the illustrated preferred embodiment is configured as a needle jet and preferably has a diameter between 0.1 and 2 mm. The inner cavity 2 with a substantially larger diameter of 3 mm to 50 mm connects to the dosing device 1 as an inlet 8 of the inner cavity 2. Due to the diameter surge directly behind the inlets 8 to the diameter of the inner cavity 2, the liquefied gas evaporates instantaneously when entering the inner cavity 2 while generating coldness, and a portion of the liquefied gas freezes into small particles. Therefore, the inner cavity 2 is also designated as expansion cavity.

At another longitudinal end, the inner cavity 2 is defined by an outlet opening which is arranged downstream. From the inlet 8 of the inner cavity 2 to the outlet opening 9, the diameter of the expansion cavity 2 expands continuously in flow direction and is preferably between 5 mm and 70 mm at the outlet opening 9. During the flow through the inner cavity 2, the particular particles agglomerate with other particles. Therefore, the inner cavity 2, which represents the expansion cavity, is also designated as agglomeration cavity. An acceleration nozzle 5 connects directly to the outlet opening 9 of the expansion cavity 2 and to the outer cavity 6, wherein the acceleration nozzle initially converges in flow direction and protrudes into the outlet opening of the expansion cavity 9. The acceleration nozzle 5 has a diameter of preferably 2 to 20 mm at its tightest spot. Because the outer contour of the expansion cavity 2 in the portion of its outlet opening 9 has a smaller diameter than the diameter of the inner contour in the transition portion between the inner contour of the outer cavity 6 and the inlet of the acceleration nozzle 5, this yields an annular carrier gas outlet 10 into the acceleration nozzle 5, which is simultaneously the outlet of the outer cavity 6.

The inner cavity 2 is configured movable in axial direction with respect to the longitudinal axis of the acceleration nozzle 5 and leads into the acceleration nozzle 5 that converges at this location. Thus, the cross-section of the carrier gas inlet 10 into the acceleration nozzle 5 can be varied through longitudinal movement of the inner cavity 2. The carrier gas inlet 10 includes a variably adjustable distance between 0 and 20 mm, preferably transversal to the longitudinal axis of the device, depending on the position of the outlet opening 9 within the device between the outer edge of the outlet opening 9 of the inner cavity 2 and the inner wall of the outer cavity 6 or the acceleration nozzle 5. In order to prevent particle accumulations, an inner wall of the expansion cavity 2 is e.g. provided with an anti-adhesion coating 12 including polytetrafluorethylene (PTFE). An anti- adhesion coating of this type can also be externally applied to the wall 1 1 which encloses the expansion cavity 2. An anti-adhesion coating 13 including e.g. PTFE is also applied to the inner wall of the acceleration nozzle 5. Furthermore, the acceleration nozzle 5 is provided with a heater 14 which includes integrated resistive heating wires. A heater of this type can also be integrated into the wall 1 1 which encloses the expansion cavity 2.

The carrier gas supply 3 is also provided with a heater 15 in order to be able to heat the carrier gas in a controlled and regulated manner during operations.

Furthermore, the expansion cavity 2 includes an additional gas supply 16 which leads into the expansion cavity 2 in order to be able to supply additional gas to the expansion cavity 2 during operations or for controlling the flow velocity in the interior of the expansion cavity 2. FIG. 2 illustrates a sectional view through the C0₂ snow blasting nozzle similar to FIG. 1 , however, without the means for preventing particle accumulations. The inventors have found that accumulations can occur in the portions A, B, C illustrated in FIG. 2, wherein the accumulations in turn can lead to a plugging of the nozzle.

The designation (A) designates an embodiment of an accumulation of solid C0₂ at the inner wall of the expansion cavity 2. When this accumulation comes loose, this can cause an inhomogeneous jet configuration or it can cause a plugging of the acceleration nozzle 5.

The designation (B) characterizes an accumulation at an outer wall of the expansion cavity 2. Through the strong cooling of the expansion cavity 2, humidity from the carrier gas can accumulate in this location. This may lead to a change in flow conditions or to a plugging of the acceleration nozzle 5.

The reference numeral (C) characterizes an accumulation at the inner wall of the acceleration nozzle 5. Through the strong cooling during the blasting process, moisture from the carrier gas or solid C0₂ or a mix of both can accumulate at this location. This may influ- ence the flow conditions or may completely plug the acceleration nozzle.

In Fig. 3, a perspective view of a device 20 for pressure blasting is shown. The device has a nozzle portion 22 in front of an outer tube 24. At a rear end of the outer tube 24, an inlet portion 26 of device 20 is shown. Attached to inlet portion 26 is a magnetic valve 28 for controlling C0₂ inlet. Fig. 4 depicts device 20 in a longitudinal cross-sectional view. From Fig. 4, it can be taken that nozzle portion 22 houses an acceleration nozzle 5. Nozzle portion 22 is attached to outer tube 24 such that nozzle portion 22 can be exchanged depending on workpiece and other requirements. However, when in place, nozzle portion 22 is attached to outer tube 24 in a fixed spatial manner. Outer tube 24 further houses a tube-like insulation layer 30 preferably made from PTFE. The insulation layer 30 encloses outer cavity 6. Outer cavity has an inlet opening 32 and an annular outlet opening 34 forming a ring nozzle. A front face of insulation layer 30 directly abuts the nozzle portion 22. The rear portion 36 of insulation layer 30 is slidably received in an inlet cavity 38 of inlet portion 26. Inlet cavity 38 is connected to carrier gas supply 3, so that a carrier gas, for instance pressurized air, can flow via carrier gas supply 3 via inlet chamber 38, outer cavity 6 to acceleration nozzle 5 where it can exit to the outside of device 20.

Within the outer cavity 6, an expansion tube 40 made from PTFE is arranged that encloses the inner cavity 2 and that extends from the inlet portion 26 into the acceleration nozzle 5 enclosed by nozzle portion 22. The expansion tube 40 forms the wall 1 1 that sepa- rates the outer cavity or chamber 6 from the inner cavity or chamber 2. The expansion tube 40 is firmly attached to the inlet portion 26. Between an outer surface of the expan- sion tube 40 and an inner surface of the insulation layer 30, an annular gap is provided that defines the outer cavity 6.

An inner surface of expansion tube 40 encloses the inner cavity 2. The inner cavity 2 has a continuously expanding portion 42 that opens into expansion nozzle 5. At the other longitudinal end of expansion tube 40, a dosing device 1 with a needle jet (needle valve nozzle) comprising a jet needle 44 for dosing the C0₂ gas stream is provided. Downstream of dosing device 1 , a liquid gas supply line 46 is provided that ends at an inlet 8 into the inner cavity 2. Thus, liquid C0₂ can be fed to dosing device 1 and will flow through supply line 46 into the inner cavity 2 (expansion chamber), where it expands. The expanded and thus frozen C0₂ further flows through the inner cavity 2 into the acceleration nozzle 5, where it comes together with the carrier gas stream at a ring nozzle formed between an inner surface of the acceleration nozzle 5 and the front-facing end of expansion tube 40.

The gap between the outer surface of expansion tube 40 at its front end and the inner surface of the acceleration nozzle 5 - that is the annular gap that forms the ring nozzle - can be adjusted through relative movement between nozzle portion 22, outer tube 24 and insulation layer 30 on one hand and expansion tube 40 and inlet portion 26 on the other hand. This relative movement in axial direction of the device pieces is achieved by rotating the outer tube 24 relative to the inlet portion 26. A helical join between the outer tube 24 and the inlet portion 26 transforms rotation of outer tube 24 into an axial movement of the outer tube 24 together with the insulation layer 30 and the nozzle portion 22. To allow such axial relative movement, end 36 of insulation layer 30 is slidably received within the inlet portion 26 of device 20.

Because the insulation layer 30 and the expansion tube 40 are made from PTFE, it is provided that the inner surface of insulation layer 30 and, thus, the outer wall of the outer cavity 6 as well as the inner wall of outer cavity 6 and the wall enclosing inner cavity 2 have non-adhesive surfaces, thus effectively avoiding undesirable particle agglomerations thereon.

Further, the helical joint between inlet portion 26 and the outer tube 40 allows for an easy adjustment of the ring nozzle and, therefore, the operation behavior of the device by simply turning the outer tube 24. A further adjustment to particular operation requirements can be achieved by adjusting the incoming liquid C0₂ flow by moving needle 44 of the needle valve of the dosing device 1 that is integrated into inlet portion 26.

Additionally, nozzle portion 22 can be exchanged for a different nozzle portion having a differently shaped acceleration nozzle 5. To allow for such an exchange of the nozzle portion, a screw-on sleeve 50 is provided at the front end of outer tube 24. The screw-on sleeve 50 can be unfastened from outer tube 24, thus allowing an exchange of nozzle portion 22.

Claims

Patent Claims

1 . A method for generating a mixed jet including frozen particles, in particular C02 particles and a carrier gas comprising the steps: introducing a liquefied gas into an expansion cavity for generating a flow of agglo- merated frozen particles from the liquefied gas; supplying the flow of agglomerated particles and a carrier gas flow to an acceleration nozzle for generating and accelerating a mixed gas jet including the frozen particles and the carrier gas, wherein the pressure dew point is lowered so that there are no particle agglomera- tions in the expansion cavity and/or the acceleration nozzle.

2. A method for generating a mixed jet including frozen particles, in particular C02 particles and a carrier gas comprising the steps: introducing a liquefied gas into an expansion cavity for generating a flow of agglomerated frozen particles from the liquefied gas; supplying the flow of agglomerated particles and a carrier gas flow to an acceleration nozzle for generating and accelerating a mixed gas jet including the frozen particles and the carrier gas, wherein a wall of the expansion cavity and/or of the acceleration nozzle is heated.

3. A method for generating a mixed jet including frozen particles, in particular C02 particles and a carrier gas comprising the steps: introducing a liquefied gas into an expansion cavity for generating a flow of agglomerated frozen particles from the liquefied gas; supplying the flow of agglomerated particles and a carrier gas flow to an acceleration nozzle for generating and accelerating a mixed gas jet including the frozen par- tides and the carrier gas, wherein an additional gas flow is introduced in the form of an additional gas for increasing and/or controlling the flow velocity in the interior of the expansion cavity.

The method according to claim 3, wherein the liquefied gas is C02 and gaseous C02 is used for an additional gas for increasing and/or controlling the flow velocity in the interior of the expansion cavity.

The method according to claim 3 or 4, wherein the additional gas flow is used for flushing the expansion cavity after the nozzle is turned off.

The method according to one of the claims 1 through 5 wherein the carrier gas is heated.

A device for pressure blasting through a mixed jet including particles of a frozen gas and a carrier gas, the device comprising: an expansion cavity (2) which includes an inlet (8) for introducing a liquefied gas into an expansion cavity (2) at its longitudinal upstream end and an outlet opening (9) at its downstream longitudinal end, wherein the outlet opening (9) has a much larger cross-section than the inlet opening (8); at least one liquid gas supply (7) which is connected with the inlet (8) of the expansion cavity (2); a carrier gas supply; and an acceleration nozzle (5) which connects to the outlet opening (9) of the expansion cavity (2) downstream and initially converges in flow-direction and which is connected with outlet opening (9) of the expansion cavity (2) and the carrier gas supply (3), wherein a wall (1 1) of the expansion cavity (2) and/or a wall of the acceleration nozzle (5) has an anti adhesive surface (12, 13).

8. A device for pressure blasting through a mixed jet including particles of a frozen gas and a carrier gas, the device comprising: an expansion cavity (2) which includes an inlet (8) for introducing a liquefied gas into an expansion cavity (2) at its longitudinal upstream end and an outlet opening (9) at its downstream longitudinal end, wherein the outlet opening (9) has a much larger cross-section than the inlet opening (8); at least one liquid gas supply (7) which is connected with the inlet (8) of the expansion cavity (2); a carrier gas supply; and an acceleration nozzle (5) which connects to the outlet opening (9) of the expansion cavity (2) downstream and initially converges in flow-direction and which is connected with outlet opening (9) of the expansion cavity (2) and the carrier gas supply (3), wherein a wall (1 1) of the expansion cavity (2) and/or a wall of the acceleration nozzle (5) is provided with a heater for heating the wall.

9. A device for pressure blasting through a mixed jet including particles of a frozen gas and a carrier gas, the device comprising: an expansion cavity (2) which includes an inlet (8) for introducing a liquefied gas into an expansion cavity (2) at its longitudinal upstream end and an outlet opening (9) at its downstream longitudinal end, wherein the outlet opening (9) has a much larger cross-section than the inlet opening (8); at least one liquid gas supply (7) which is connected with the inlet (8) of the expansion cavity (2); a carrier gas supply; and an acceleration nozzle (5) which connects to the outlet opening (9) of the expansion cavity (2) downstream and initially converges in flow-direction and which is connected with outlet opening (9) of the expansion cavity (2) and the carrier gas supply (3), wherein means (15) are provided for adjusting and/or lowering a pressure dew point of the carrier gas

10. The device according to claim 9, wherein a carrier gas heater (15) is provided for adjusting and/or lowering the pressure dew point of the pressure gas.

1 1 . A device for pressure blasting through a mixed jet including particles of a frozen gas and a carrier gas, the device comprising: an expansion cavity (2) which includes an inlet (8) for introducing a liquefied gas into an expansion cavity (2) at its longitudinal upstream end and an outlet opening (9) at its downstream longitudinal end, wherein the outlet opening (9) has a much larger cross-section than the inlet opening (8); at least one liquid gas supply (7) which is connected with the inlet (8) of the expansion cavity (2); a carrier gas supply; and an acceleration nozzle (5) which connects to the outlet opening (9) of the expansion cavity (2) downstream and initially converges in flow-direction and which is connected with outlet opening (9) of the expansion cavity (2) and the carrier gas supply (3), wherein an additional gas supply (16) opens into the expansion cavity (2) in order to be able to supply an additional gas to the expansion cavity (2) during operations for increasing or controlling the flow velocity in the interior of the expansion cavity (2).

The device according to one of the claims 7 through 10 comprising: a nozzle housing (4) which encloses an outer cavity (6) and an inner cavity (2), wherein the inner cavity (2) forms the expansion cavity, wherein the outer cavity (6) envelops the inner cavity (2) at least partially in the portion of the outlet opening (9), wherein the carrier gas supply (3) is connected with the outer cavity (6), and wherein the acceleration nozzle (5) includes a carrier gas inlet (10) for an outlet of the outer cavity (6), wherein the carrier gas inlet is arranged laterally with respect to the outlet opening (9) and includes a variably adjustable cross section.

13. The device according to claim 12, wherein the carrier gas inlet (10) is arranged in an annular manner between the outlet opening (9) of the expansion cavity (2) and a wall of the acceleration nozzle that converges in flow-direction.