GB2454659A

GB2454659A - Cleaning poultry trays using solid carbon dioxide pellets

Info

Publication number: GB2454659A
Application number: GB0722173A
Authority: GB
Inventors: Simon Handley
Original assignee: BOC Group Ltd
Current assignee: BOC Group Ltd
Priority date: 2007-11-13
Filing date: 2007-11-13
Publication date: 2009-05-20
Also published as: GB0722173D0

Abstract

A method of cleaning poultry transport trays comprises impacting pellets of solid carbon dioxide on surfaces of the trays to be cleaned. Excreta, bacteria and pathogens are thereby removed from the trays. An apparatus for performing the method comprises a tunnel 2, a conveyor 8 for advancing the trays through the tunnel 2, and rows 10, 12 and 14 of nozzles 11 for propelling pellets of solid carbon dioxide at all surfaces of the trays.

Description

METHOD OF AND APPARATUS FOR CLEANING

This invention relates to a method of an apparatus for cleaning fouled poultry trays.

A preferred method of transporting live birds from farm to place of slaughter is by the use of poultry transport trays. These trays are typically made of a robust plastics material, can be stacked with poultry therein and have walls that retain the poultry.

The walls and base of each tray have a sufficient open area to ensure that the birds do not suffocate during transport.

The trays are typically, in use, loaded with live birds and then stacked onto a flat bed lorry. During transport, the birds foul the trays. As a result of the fouling of the trays, films containing potentially harmful bacteria (biofilms') can be formed. After transport, the birds are removed and the trays are washed to remove soil. Typically, high pressure water jets are used to wash the fouled trays. Once the trays have been washed they are stacked back onto the lorry and returned to the poultry farm for use again. The trays at this stage are still wet and notwithstanding the washing are liable to carry pathogens. The water jets seem particularly ineffective in removing biofilms. A common example of a pathogen which is not eradicated by washing is the Campylobacter bacterium.

There is therefore a need for an improved method of ar1 apparatus for cleaning fouled poultry trays.

According to the present invention there is provided a method of cleaning poultry trays, comprising impacting pellets of solid carbon dioxide on surfaces of the trays to be cleaned.

The invention also provides apparatus for cleaning poultry trays comprising a tunnel, means for advancing poultry trays to be cleaned through the tunnel, and means for propelling pellets of solid carbon dioxide against surfaces of the trays to be cleaned, the propelling means being arranged and configured to cause pellets of solid carbon dioxide to impact on the surfaces of the trays to be cleaned.

We have surprisingly found that impact of solid carbon dioxide pellets is capable of removing pathogens such as the Campylobacter bacterium.

Pellets of solid carbon dioxide are readily commercially available. The terms "pellets of carbon dioxide" or "carbon dioxide pellets" are used herein to mean particulate bodies of compressed or compacted carbon dioxide snow. Carbon dioxide snow is, for example, formed by ejecting liquid carbon dioxide at a suitable pressure through a nozzle. The liquid carbon dioxide is transformed into a solid snow-like substance and a cold gas. The untreated snow is not sufficiently hard for it to be a suitable abrasive material for use in the method and apparatus according to the invention. The particles of snow may be compacted or compressed together to form pellets by means well known in the art.

The precise size of the carbon dioxide pellets is not critical to the invention, but it is desirable that more than 50% by number of the pellets have a diameter of at least 3mm. If desired, smaller particles of a different abrasive medium, such as a ceramic, can be used as a projectile in addition to the solid carbon dioxide pellets.

The surfaces of the trays to be cleaned may bear foul deposits or potentially hazardous biofilms.

The carbon dioxide pellets are preferably blasted at the surfaces of the trays to be cleaned, that is to say they are projected at a high velocity at the surfaces to be cleaned. The velocity is preferably at least lOOm/s and may, if desired, be supersonic. In order to create the high velocity, a flow of a carher gas stream under a pressure typically in the range of 2 to 25 bar is created, preferably 5 to 20 bar, the pellets fed into the carrier gas stream, and the carrier gas stream, laden with solid carbon dioxide pellets, is ejected from one or more nozzles (which nozzles provide the said means for propelling the pellets of solid carbon dioxide). Preferably, a plurality of such nozzles is provided.

The trays are preferably translated relative to the nozzles. Typically, the trays are transported along a path and the nozzles retain a fixed position. It is possible, however, to keep the trays in fixed position and to translate the nozzle or nozzles.

Alternatively, both the nozzle(s) and the trays may be translated. -3--

Preferably at least one of the nozzles is adapted to swivel. The or each swivelling nozzle may make a ball and socket union with a pipe from which the carbon dioxide pellets are supplied. If desired, the or each swivelling nozzle may be caused to swivel by a suitable arrangement of a motor and a transmission means. Preferably, however, the or each nozzle is preferably configured so as to be self-swivelling.

An array of nozzles is preferably provided within the tunnel so as to ensure that all surfaces, both internal and external, of the trays are impacted by the solid carbon dioxide pellets. The use of swivelling nozzles helps to achieve this result.

The tunnel preferably has an endless conveyor adapted to advance the trays through the tunnel. The conveyor preferably comprises a belt having a percentage open area of at least 80%. Having such a high percentage open area facilitates the cleaning from below of the bottom exterior surfaces of the trays.

The tunnel preferably has a port (typically at its top) for the extraction of carbon dioxide vapour. Airborne particulate material, typically disengaged from the surface of the trays by the impact on them of the carbon dioxide pellets, are typically extracted with the carbon dioxide vapour. An extractor fan is preferably associated with the outlet port. To this end, the tunnel preferably has an exhaust hood over the outlet port, the extractor fan being disposed within the hood. The extractor fan, in operation, preferably draws exhaust gas through a filter to remove gas borne particles.

The bombardment of fouled areas of the trays with solid carbon dioxide pellets tends to create some particulate waste. The exhaust hood is therefore preferably provided with a filter for the removal of such particulate waste or debris. The filter is preferably provided upstream of the extractor fan. If desired, other atmosphere conditioning or cleaning means may be provided in the hood. The extractor fan preferably discharges into a duct which has an outlet remote from any area accessible to people.

The cleansed trays are preferably subjected to impact with high velocity jets of air so as to dislodge dust and other debris to facilitate their extraction by the fan.

Accordingly the tunnel is preferably provided with at least one additional nozzle for diverting a jet of gas, laden with solid carbon dioxide pellets, at the cleaned trays.

The method and apparatus according to the present invention may be employed instead of a conventional cleaning apparatus employing high velocity water jets.

The method and apparatus according to the invention will now be described by way of example with reference for the accompanying drawings, in which: Figure 1 is a schematic sectional side elevation of a tray cleaning tunnel; Figure 2 is a schematic end elevation of the tunnel shown in Figure 1; and Figure 3 is a schematic view of part of a conveyor belt employed in the apparatus shown in Figure 1.

Referring to the drawings, an elongate tunnel 2 has an inlet 4 and an outlet 6. The tunnel 2 is provided with an endless conveyor 8. For ease of illustration, only the upper run of the conveyor 8 is shown in the drawings. The conveyor 8 has a lower run (not shown) and extends around a driven wheel (not shown) and an idler wheel (not shown) at opposite ends thereof. The tunnel 2 is associated with means for driving the former of these wheels. The drive means is typically located outside the tunnel 2 in view of the fact that sub-ambient freezing temperatures are created within the tunnel 2 during its operation.

The tunnel 2 is provided with a first row 10 of nozzles 11 positioned above the upper run of the conveyor 8. There is sufficient clearance for fouled poultry trays carried by the conveyor 8 to pass thereunder. The row 10 of nozzles 11 extends from a region within the tunnel 2 near its inlet 4 to a region within the tunnel 2 near its outlet 6.

There is a complementary second row 12 of nozzles 11 within the tunnel 2 positioned beneath the upper run of the conveyor 8 but above the lower run (not shown).

A third row 14 of nozzles ills provided along one side of the tunnel 2 from a region near its inlet 4 to a region near its outlet 6. There is a complementary fourth row of nozzles (not shown) on the opposite side of the tunnel 2.

Each of the nozzles 11 communicates with a carrier gas stream, preferably air at a pressure of approximately 10 bar, into which pellets of carbon dioxide (preferably having a size of approximately 10mm) are fed from, for example, a hopper (not shown) having a rotary valve (not shown) at its bottom for the discharge of pellets from the hopper into the carrier gas. In one arrangement, each row of nozzles may be served by a common conduit (not shown). Each conduit may have a dedicated hopper and supply of carrier gas. Alternatively, there may be a single hopper and a single supply of carrier gas with which the four common conduits communicate. If a common supply of carrier gas is used, allowance needs to be made for pressure drop along the particle conveying network. The arrangement is such that each nozzle projects the pellets of solid carbon dioxide at a velocity of at least 100 metres per second and typically in the order of 200 to 300 metres per second. The rows of nozzles are arranged so that the upper row 10 directs pellets of carbon dioxicb at the bottom forward and rearward internal surfaces and the forward and rearward external surfaces of the trays (indicated by the reference 16 in the drawings) as they are advanced through the tunnel 2 on the conveyor 8. Preferably, the nozzles in the row swivel so as to facilitate the cleaning of these surfaces. Most preferably, the nozzles in the row 10 are self-swivelling.

The nozzles in the row 12 are arranged and configured so as to propel pellets of solid carbon dioxide against the exterior surface or surfaces at the base of each soiled tray 16 as it passes through the tunnel 2. Similarly to the nozzles in the row 10, the nozzles in the row 12 may be swivelling, preferably self-swivelling. The nozzles in the side rows 14 are arranged and configured to propel pellets of solid carbon dioxide at the internal and external side surfaces of the trays 16 as they are advanced o through the tunnel 2 by the conveyor 8. The rows of nozzles 11 are deployed such that, in use, all internal and external surfaces of the trays are subjected to impact by the high velocity pellets of carbon dioxide.

As shown in Figure 3, the conveyor 8 has a belt comprising equally spaced rods 20 extending between continuous, opposed sides 22 and 24. If desired, the sides 22 and 24 may be articulated. The spacing of the rods 20 is such as to ensure that carbon dioxide pellets from the bottom row 12 of nozzles are able mainly to pass through the upper run of the conveyor belt 8 and strike the bottom exterior surface or surfaces of each soiled tray 16 passing through the tunnel 2. Preferably, the conveyor belt has an effective percentage open area of at least 80%.

In operation of the tunnel 2 shown in the drawings cold carbon dioxide vapour is formed by sublimation of the solid carbon dioxide pellets. There is thus a need to extract the cold carbon dioxide vapour from the tunnel 2. In addition, the impact of the pellets of solid carbon dioxide against soiled areas of the trays 16 tends to cause minute particles of dust to be formed. The tunnel 2 is provided at its outlet end with a port 30 in its roof. The port 30 communicates with a hood 32 defining an outlet duct 34 for carbon dioxide vapour ladened with particles of dust. The hood 32 is provided with a fan 36 which is operable to extract the dust-ladened carbon dioxide from the interior of the tunnel 2. The hood 32 is preferably provided with a filter 38 either above or beneath the fan 36 so as to disengage particles of dust from the vapour being extracted.

The used pellets of carbon dioxide collect at the bottom of the tunnel 2. There is typically no need to extract the used pellets as they sublime naturally. The sublimation of the pellets has the effect of chilling the atmosphere within the tunnel 2.

In general, the tunnel 2 is operated such that the chilling effect of the carbon dioxide pellets is not sufficient to create a sub-zero (degrees Celsius) atmosphere in the tunnel, thereby ensuring that spent pellets will readily vaporise again. There is therefore no need to provide a means for recovering spent pellets of carbon dioxide from the tunnel. There is a tendency for some solid particles of dust to remain in the cleaned tray or adhering to surfaces thereof. Such particles may be dislodged by direction of at least one high velocity jet of air or other gas at the cleaned trays at a region near the exit 6 from the tunnel 2. Preferably, there is a first air jet provided from a nozzle 40 located above the upper run of the conveyor 8 and a second nozzle for forming an air jet below the upper run of the conveyor 8. The effect of the air jet is to dislodge such particles of dust from the trays causing them to become entrained in the atmosphere within the tunnel 2 and to be extracted by the fan 36.

-7---In operation, the conveyor 8 typically passes 450 trays per hour through the tunnel 2 for cleaning. The cleaned tray may be then subjected, if desired, to conventional washing. After use, the tunnel 2 is preferably cleaned by means of high pressure water jets. Typically, the tunnel is provided with its own cleaning system, which may utilise high pressure water jets and which may also utilise ozone for the purpose of destroying any resident bacterial in the tunnel.

Claims

1. A method of cleaning poultry trays, comprising impacting pellets of solid carbon dioxide on surfaces of the trays to be cleaned.

2. A method according to claim 1, in which the pellets of solid carbon dioxide have a velocity of at least lOOm/s.

3. A method according to claim 1 or claim 2, in which more than 50% by number of the pellets have a diameter of at least 3mm.

4. A method according to any one of the preceding claims, in which the pellets are ejected from at least one nozzle and are carried to the nozzle in a carrier gas stream.

5. A method according to claim 4, in which the nozzle or at least one of the nozzles is adapted to swivel.

6. A method according to claim 4 or claim 5, in which the nozzles are self-swivelling.

7. Apparatus for cleaning poultry trays, comprising a tunnel, means for advancing poultry trays to be cleaned through the tunnel, and means for propelling pellets of solid carbon dioxide against surfaces of the trays to be cleaned, the propelling means being arranged and configured to cause pellets of solid carbon dioxide to impact on the surfaces of the trays to be cleaned.

8. Apparatus according to claim 7, wherein the means for propelling the pellets of solid carbon dioxide comprises a plurality of nozzles.

9. Apparatus according to claim 8, wherein there is an array of nozzles arranged to ensure that, in use, all surfaces, both internal and external, of the trays are impacted by the solid carbon dioxide pellets.

10. Apparatus according to claim 8 or claim 9, in which at least one of the nozzles is adapted to swivel.

11. Apparatus according to any one of claims 8 to 10, in which at least one of the nozzles is self-swivelling.

12. Apparatus according to any claims 7 to 11, wherein the means for advancing fouled poultry trays through the tunnel comprises an endless conveyor.

13. Apparatus according to claim 12, in which the endless conveyor comprises a belt having a percentage open area of at least 80%.

14. Apparatus according to any one of claims 7 to 13, wherein the tunnel has a port for the extraction of carbon dioxide vapour.

15. Apparatus according to claim 14, wherein an extractor fan is associated with the port.

16. Apparatus according to claim 15, wherein the tunnel has an exhaust hood over the part, the extractor fan being disposed within the exhaust hood.

17. Apparatus according to claim 16, wherein the exhaust hood is provided with a filter for the removal of particulate debris.

18. Apparatus according to any one of claims 7 to 17, wherein the tunnel is provided with at least one additional nozzle for directing a jet of gas, at the cleaned trays.