WO2007003202A1

WO2007003202A1 - System and method for cleaning of a surface

Info

Publication number: WO2007003202A1
Application number: PCT/DK2006/000398
Authority: WO
Inventors: Stoker Hammer Søren
Original assignee: Cryocip A/S
Priority date: 2005-07-06
Filing date: 2006-07-05
Publication date: 2007-01-11
Also published as: WO2007003201A1

Abstract

A system (5, 6) for cleaning of surfaces is disclosed, in particular of a food processing system (1) , by means of blasting with solid carbon dioxide particles with high velocity, so that impurities on the surface of the system or equipment are frozen and by abrasive action of the particles removed from the surface. The system comprises a first shielding member having a rim enclosing a surface to be cleaned and a second shielding member having a rim enclosing the rim of the first shielding member, forming a cavity between the shielding members. A jet of solid carbon dioxide particles and the carrier gas is delivered from the nozzle within said first shielding member towards the surface to be cleaned. The pellets will evaporate completely or at least partially, and the evaporated carbon dioxide will together with carrier gas and loosened debris be sucked out under the rim of the first shielding member and into the cavity between the shielding members .

Description

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SYSTEM AND METHOD FOR CLEANING OF A SURFACE

The present invention relates to cleaning of surfaces, in particular of a food processing system, by means of blasting with solid carbon dioxide particles with high velocity, so that impurities on the surface of the system or equipment are frozen and by abrasive action of the particles removed from the surface.

BACKGROUND

Cleaning of surfaces in equipment in food processing systems, such as of the floor, tables, conveyers etc. is normally performed with hot water containing an aggressive detergent, followed by a treatment with hot clean water for removing the impurities as well as remaining detergent, which is normally not compatible with the use for food processing. Finally, remaining water must be removed from the surface, e.g. by blowing heated air onto the surface.

However, such cleaning procedure render the food processing equipment out of normal operation for an extended period of time, which is disadvantageous. Furthermore, the cleaned equipment is heated to a temperature higher than the one suitable for operation, at least for a number of food processing systems, and even more time and energy is spend on lowering the temperature to the normal operating temperature of the equipment.

The use of blasting with solid carbon dioxide particles for cleaning purposes is well- known in the art, e.g. from EP 1 054 752, where the method is applied to a kitchen ventilation duct for the removal of grease by means of a nozzle mounted on a trolley which is driven through the duct.

In US 5,932,026, in DE 195 35 557 and in DE 102 15 216, different arrangements for the cleaning of internal surfaces are disclosed, which have in common that the nozzle for the blasting with solid carbon dioxide particles is mounted on an arm that during the blasting process is moved around within the cavity so that the full surface may be reached and cleaned by the jet of particles expelled from the nozzle.

The known systems provides for either cleaning inside a confined or closed space, where the debris may be removed by the circulation of gas through the space or simple blasting, where the loosened debris is spread in the environment.

It is an object of the present invention to provide a device and a method for cleaning surfaces where the loosened debris is controlled and may be removed from the area of the surface in a controlled manner.

BRIEF DESCRIPTION OF THE INVENTION

The present invention solves the problem by providing a system for cleaning of a surface, the system comprising a first shielding member having a rim enclosing a surface to be cleaned and extending at a first distance, such as 8 to 30 millimetres from said surface, a second shielding member having a rim enclosing the rim of the first shielding member and extending at a second distance, so that a cavity is defined between the first shielding member and the second shielding member, suction means connected to said cavity, a nozzle arranged within said first shielding member and directed towards the surface, and means for providing a pressurised flow of solid carbon dioxide particles together with a carrier gas to the nozzle, preferably pressurised, clean atmospheric air,

The carrier gas may alternatively be carbon dioxide gas or nitrogen gas, which are both substantially inactive with respect to organic material.

A jet of solid carbon dioxide particles and the carrier gas is delivered from the nozzle towards the surface to be cleaned, preferably a substantially plane surface such as a floor or the surface of a conveyor belt, within the rim of the first shielding member. The impact of the particles, or pellets, on the surface freezes the debris to be removed from the surface to a temperature close to the temperature of the pellets, about -78⁰C, where the debris will be very hard and brittle, and the following pellets will loosen the debris from the surface. The pellets will evaporate completely or at least partially, and the evaporated carbon dioxide will together with carrier gas and loosened debris be sucked out under the rim of the first shielding member and into the cavity between the first and the second shielding members by means of the suction means. Thus, an effective local cleaning effect is obtained, where the loosened debris is removed in a controlled manner.

The rim of the second shielding member is preferably arranged at a closer distance, i.e. the second distance, such as 1 to 5 millimetres from said surface that the rim of the first shielding member, i.e. the first distance, so that the amount of air drawn in from the exterior of the second shielding member is reduced to a minimum. In a particular embodiment, the rim of the second shielding member is equipped with brushes or a similar flexible material, so that the rim is in actual contact with the surface to be cleaned.

Thus, the second distance is preferably shorter than the first distance and the difference is in a preferred embodiment of the present invention within the range of 5 to 30 millimetres, preferably within the range of 8 to 20 millimetres.

The two shielding members are preferably so arranged, that the cavity defined between them has a width of 2 to 10 centimetres, preferably between 3 and 7 centimetres along most of the rim of the first shield.

In one particular embodiment, the nozzle is arranged rotatably about an axis substantially perpendicular to the surface and rotation of the nozzle is during operation of the system driven by a separate motor or by the flow of the solid carbon dioxide particles and the carrier gas.

In a second particular embodiment, the nozzle is arranged to oscillate during operation of the system so that the jet from the nozzle cleans a larger area of the surface.

Other advantages of the present invention will be apparent from the following description.

In a specific embodiment of the present invention, the system further comprises means to supply compressed air solely through the nozzle, alternatively or additionally means to supply compressed gaseous carbon dioxide solely through the nozzle. This flow of gas may be used to blow any remaining debris away from the surface, and a flow of carbon dioxide may in particular also be employed to cool down the surfaces prior to cleaning with the application of solid particles of carbon dioxide. In a preferred embodiment, the system comprises a manifold having means for selectively providing a flow of particles with a carrier gas, a flow of gaseous carbon dioxide solely and a flow of atmospheric air through the nozzle.

In yet a preferred embodiment, the means for providing a flow under pressure of solid carbon dioxide particles together with a carrier gas to the nozzle comprises a source for pressurised gaseous carbon dioxide, means for preparing solid carbon dioxide particles from pressurised gaseous carbon dioxide from said source, a conduit connecting said source and said means for preparing solid carbon dioxide particles, and a conduit connecting said means for preparing solid carbon dioxide particles and said nozzle. Thus, the apparatus for producing the solid carbon dioxide particles or pellets provided to the nozzle is coupled directly to the nozzle so as to enable the provision of a large flow of particles to the nozzle. The means for preparing the solid carbon dioxide particles comprises preferably means to produce carbon dioxide snow and means to compress said snow with a pressure in the range of 160 to 650 bar, preferably in the range of 200 to 350 bar, so as to form said particles having an advantageous quality for the present use. The means for preparing the particles are preferably designed to prepare particles of a diameter in the range of 1.7 mm to 8 mm, preferably in the range of 2.5 mm to 6 mm.

Furthermore, the system has in a preferred embodiment of the present invention an exit flow cleaning circuit coupled to the suction means of the system, the circuit comprising a cyclone separator and a blower, wherein the outlet of the cyclone separator is coupled to the inlet of the blower, and the outlet of the blower is coupled to the inlet of the cyclone separator via a constriction, which reduces the cross- sectional flow area with a factor of at least two, and the outlet of the cavity being coupled to the arrangement between the constriction and the inlet to the cyclone separator, the circuit also comprising an outlet for the exit of a part of the flow circulated in the circuit. By providing a recirculation of at least a part of the gas from the outlet of the cyclone separator and via the blower to the inlet of the separator, an increased gas flow together with the flow of solid debris is formed, whereby the efficiency of the cyclone separator in separating the solid debris is improved.

The system comprises in yet a preferred embodiment of the present invention means for providing a carrier gas to the nozzle with a pressure of between 5 bar and 20 bar, preferably between 8 bar and 13 bar above atmospheric pressure, and in an amount of between 3 m³ and 20 m³ per minute, preferably between 6 m³ and 15 m³. The pressure at the outlet of the cavity is lower to provide a flow through the cavity, preferably between atmospheric pressure and -0.7 bar below that.

The means for providing a pressurised flow of solid carbon dioxide particles together with a carrier gas to the nozzle are likewise in a preferred embodiment suitable for providing a flow of solid carbon dioxide particles in the range of 25 to 150 kg per hour, preferably in the range of 40 to 120 kg per hour. The present invention also relates to a method for cleaning of surfaces, in particular of a food processing system, by means of the steps discussed above, which e.g. could be performed with the system of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention are illustrated in the enclosed drawings, wherein

Fig. 1 is a perspective view of an embodiment of the present invention,

Fig. 2 is a first cross-sectional view of the device of Fig. 1,

Fig. 3 is a second cross-sectional view of the device of Fig. 1,

Fig. 4 is a perspective view of another embodiment of the present invention,

Fig. 5 is a partly cut-away side view of the device of Fig. 4,

Fig. 6 is a horizontal cross-sectional view of the device of Fig. 4, and

Fig. 7 is a schematic overview of a supply section together with a debris separation system.

The embodiments of the figures are discussed in details below. The figures are to be regarded as illustrations of particular embodiments of the present invention and not as limiting the scope of the invention and the protection as defined in the claims. DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

In Figs. 1-3, an embodiment of the present invention is illustrated for cleaning of a surface, in particular a flat surface such as a conveyor band 1, used primarily for conveyance of food products, wherein a nozzle 2 is enclosed in a first shield 3, which is closed at the top and opens towards the surface. The rim 4 of the first shield 3 is about 12 millimetres from the surface of the conveyor band 1, and the nozzle 2 is arranged to oscillate from side to side during operation as shown with arrow A in

Fig. 3, driven by the flow of the carrier gas and the solid carbon dioxide particles, whereby the full surface area below the rim 4 of the first shield 3 is cleaned by the jet from the nozzle 2.

A second shield 5 is arranged enclosing the first shield 3, so that a vertical distance of about 5 centimetres is provided between the two shields 3, 5, and suction means are via the connecting piece 6 connected to the cavity defined between the shields 3, 5 to remove the loosened debris together with the flow of carrier gas and evaporated pellets from the nozzle by suction. The two shields 3, 5 are coincident at the side 7 of the rim 4 opposing the connecting piece 6, but the opening between the shields 3, 5 along the remaining part of the rim 4 is sufficient to remove all loosened debris satisfactory.

Another embodiment of the present invention is shown in Figs. 4-6, wherein the two shields 3, 5 are arranged concentric and the nozzle 2 is arranged rotatable within the first shield 3. This embodiment is particularly suited for cleaning of larger surfaces, where the system is moved along the surface, e.g. a floor or plane walls.

A supply section for the system is shown in Fig. 7 together with a debris separation system. The nozzle 2 is provided with a flow of carbon dioxide pellets and compressed air from the outlet 8 of a supply section of the system comprising a pelletizer 9, which is supplied with liquid carbon dioxide via a tube 10 from a storage (not shown). The liquid carbon dioxide is turned into carbon dioxide snow by lowering the pressure thereof, and the snow is compressed into pellets with a compression pressure of about 250 bar provided by means of the liquid carbon dioxide. The pelletizer 9 is connected to a feeding arrangement 11, where the pellets are mixed with compressed air from an air compressor 12 which is used to feed a flow of the pellets and compressed air to the nozzle 2 via a pipeline 13.

A debris separation system is connected to the connecting piece 6. The separation system comprises a cyclone separator 14, the air outlet of which is connected to a blower 15, where the pressure of the air is increased. The separated solid and liquid debris is removed from the cyclone separator through an outlet in the bottom thereof (not shown). From the blower 15, the air passes a constriction 16 in order to accelerate the air flow by reducing the cross-sectional area of the internal opening of the tube to about a third, and thereby lower the pressure to about 0.5 bar below atmospheric pressure. The connecting piece 6is connected to the inlet 17 of the tube 18 connecting the constriction 16 and the inlet 19 of the cyclone separator 14, whereby vaporised and possibly solid carbon dioxide, air and debris are removed by suction from the connecting piece 6 into the flow of air from the constriction 16 and to the inlet 19 of the cyclone separator 14. With this arrangement, the cyclone separator 14 is operated with a higher flow of gas, i.e. atmospheric air and vaporised carbon dioxide than would be the case if the connecting piece 6 was coupled directly to the cyclone separator 14, which improves the efficiency of the separation. Also, the suction at the connecting piece 6 due to the presence of the constriction 16 and the air flow, ensures that the loosened debris is removed fromthe interior of the interior of the shields 3, 5 and the surface 1. The arrangement is equipped with a pressure-controlled outlet valve (not shown) situated right after the air outlet of the cyclone separator 14, where excess air is delivered to the environment through a bag filter.

Claims

1. A system for cleaning of a surface, comprising a first shielding member having a rim enclosing a surface to be cleaned and extending at a first distance from said surface, a second shielding member having a rim enclosing the rim of the first shielding member and extending at a second distance from said surface, so that a cavity is defined between the first shielding member and the second shielding member, suction means connected to said cavity, a nozzle arranged within said first shielding member and directed towards the surface, and means for providing a pressurised flow of solid carbon dioxide particles together with a carrier gas to the nozzle.

2. A system according to claim 1, wherein the second distance is within the range of 5 to 30 millimetres, preferably within the range of 8 to 20 millimetres shorter than the first distance.

3. A system according to claim 1 or 2, wherein the nozzle is arranged rotatably about an axis substantially perpendicular to the surface.

4. A system according to claim 1 or 2, wherein the nozzle is arranged to oscillate during operation of the system.

5. A system according to any of the preceding claims, further comprising means to supply compressed air solely through the nozzle.

6. A system according to any of the preceding claims, further comprising means to supply compressed gaseous carbon dioxide solely through the nozzle.

7. A system according to any of the preceding claims, wherein said means for providing a flow under pressure of solid carbon dioxide particles together with a carrier gas to the nozzle comprises a source for pressurised gaseous carbon dioxide, means for preparing solid carbon dioxide particles from pressurised gaseous carbon dioxide from said source, a conduit connecting said source and said means for preparing solid carbon dioxide particles, and a conduit connecting said means for preparing solid carbon dioxide particles and said nozzle.

8. A system according to claim 7, wherein the means for preparing the solid carbon dioxide particles comprises means to produce carbon dioxide snow and means to compress said snow with a pressure in the range of 160 to 650 bar, preferably in the range of 200 to 350 bar, so as to form said particles.

9. A system according to any of claims 7 or 8, wherein said means for preparing particles are designed to prepare particles of a diameter in the range of 1.7 mm to 8 mm, preferably in the range of 2.5 mm to 6 mm.

10. A system according to any of the preceding claims, wherein said suction means comprises an exit flow cleaning circuit coupled to the outlet from the cavity, the circuit comprising a cyclone separator, and a blower, wherein the outlet of the cyclone separator is coupled to the inlet of the blower, and the outlet of the blower is coupled to the inlet of the cyclone separator via a constriction, which reduces the cross-sectional flow area with a factor of at least two, and the outlet of the cavity being coupled to the arrangement between the constriction and the inlet to the cyclone separator, the circuit also comprising an outlet for the exit of a part of the flow circulated in the circuit.

11. A system according to any of the preceding claims, comprising means for providing a carrier gas to the nozzle with a pressure of between 5 bar and 20 bar, preferably between 8 bar and 13 bar above atmospheric pressure, and in an amount of between 3 m³ and 20 m³ per minute, preferably between 6 m³ and 15 m³.

12. A system according to any of the preceding claims, wherein the means for providing a pressurised flow of solid carbon dioxide particles together with a carrier gas to the nozzle are suitable for providing a flow of solid carbon dioxide particles in the range of 25 to 150 kg per hour, preferably in the range of 40 to 120 kg per hour.