WO1999027779A1

WO1999027779A1 - Apparatus and method for sterilising soil

Info

Publication number: WO1999027779A1
Application number: PCT/AU1998/000978
Authority: WO
Inventors: Charles Crowther Cope
Original assignee: Charles Crowther Cope
Priority date: 1997-11-26
Filing date: 1998-11-25
Publication date: 1999-06-10
Also published as: ZA9810814B; AR018258A1; AUPP056297A0

Abstract

An apparatus (10) for sterilising a top layer of soil (12) includes a housing (14) defining a sterilisation chamber (16) having an entry opening (18) at a front end to admit the top layer of soil (12) into the housing (14) and an exit opening (20) at an opposite end so that the entry and exit openings (18, 20) are spaced by the sterilisation chamber (16). Gas burners (28) are provided in the housing (14) for heating the sterilisation chamber (16) to a temperature effect to substantially sterilise the soil (12) passing therethrough. The top layer of soil (12) enters the housing (14) through the entry opening (18), passes through the sterilisation chamber (16) where it is substantially sterilised by the heat generated by the gas burners (28) and is then returned to the ground G through the exit opening (20).

Description

Title

APPARATUS AND METHOD FOR STERILISING SOIL

Field of the Invention

The present invention relates to an apparatus and method for sterilising a top layer of soil particularly, though not exclusively, for agricultural purposes.

Background to the Invention

In order to maximise crop yields farmers undertake extensive weed and insect control programs. This typically involves the use of herbicides and insecticides. However use of herbicides and insecticides have inherent disadvantages including:

(i) not only are they expensive per se the cost of applying them to the land is also high;

(ii) safety hazards in their physical handling;

(iii) spraying of herbicides/insecticides is environmentally unsafe; and,

(iv) the increasing resistance of weed/insects to herbicides and insecticides means they are becoming less effect or must be used in high concentrations and/or more frequently.

An alternate method for controlling ground level vegetation is described in Australian Patent No 661648. This patent discloses a method and apparatus for spraying steam at relatively high pressure onto the ground. The steam is typically at a temperature of between 100°C to 120°C and kills the weeds by breaking down their cellular structure. Clearly, most ground level insects are also killed by the steam. However, subsurface weeds, seeds and insects are largely unaffected due to the excellent thermal insulating properties of soil. Summary of the Invention

It is an object of the present invention to provide an apparatus and method for substantially sterilising a top layer of soil.

Throughout this specification the term "sterilised" or "sterilisation" or "sterilising" in relation to soil is used to describe and denote the substantial eradication of vegetation, seeds, insects, bacteria and other living organisms in the soil.

According to a first aspect of the present invention there is provided an apparatus for sterilising a top layer of soil including: a housing defining a sterilisation chamber having an entry opening at one end to admit a top layer of soil into the housing and, an exit opening at an opposite end of the housing spaced from the entry opening by the sterilisation chamber, the housing adapted for attachment to a vehicle; and heating means for heating the sterilisation chamber to a temperature effective to substantially sterilise the soil passing through the sterilisation chamber; wherein the apparatus is coupled to a vehicle and lowered to a position where the entry opening is at a predetermined depth beneath the ground level and when the vehicle is operated to traverse the ground, a top layer of soil down to that depth enters the housing through the entry opening, passes through the sterilisation chamber where it is substantially sterilised by heat from the heating means, and returned to the ground through the exit opening.

Preferably the heating means heats the sterilisation chamber to a temperature in the order of or above 700°C.

Preferably said heating means includes one or more gas burners adapted for burning gas inside the sterilisation chamber.

Preferably each gas burner comprises a manifold provided with one or more nozzles for spraying gas into the sterilisation chamber. Preferably said apparatus further includes a water injection system for spraying water onto the soil traversing the sterilisation chamber prior to passing through the exit opening.

Preferably said apparatus further includes an air injection system for injecting air into the sterilisation chamber in a general direction from the entry opening to the exit opening to assist in combustion of the gas and directing the soil into and through the sterilisation chamber.

Preferably the apparatus further includes replaceable ground engaging blades disposed about the entry opening for cutting into the ground and for directing soil into the entry opening.

Accordingly to another aspect of the present invention there is provided a method for sterilising a top layer of soil including: providing a housing defining a sterilisation chamber and having an entry opening at one end to admit a top layer of soil into the sterilisation chamber and an exit opening at an opposite end spaced from the entry opening by the sterilisation chamber; heating means for heating the sterilisation chamber to a temperature effective to substantially sterilise the soil passing through the sterilisation chamber; coupling the housing to a vehicle; and operating the vehicle to traverse the ground and simultaneously lowering the apparatus so that the entry opening is at a predetermined level beneath the ground so that the top layer of soil to that depth enters the housing through the entry opening and passes through the sterilisation chamber where it is substantially sterilised by heat, and thereafter returning the sterilised soil to the ground through the exit opening. Brief Description of the Drawings

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which;

Figure 1 is a cross sectional view from the side of an embodiment of an apparatus for sterilising soil;

Figure 2 is a sectional view for a horizontal plane of the apparatus looking upwardly at the inside of the top thereof;

Figure 3 is a view of section AA of the apparatus shown in Figure 1 ;

Figure 4 is a side view of the apparatus in use; and,

Figure 5 is a top view of the apparatus in use.

Detailed Description of the Preferred Embodiment

Referring to the accompanying drawings, an apparatus 10 for sterilising a top layer of soil 12 includes a housing 14 defining a sterilisation chamber 16 having an entry opening 18 at a front end to admit a top layer of soil 12 into the housing 14 and, an exit opening 20 at an opposite end of the housing 14 so that the entry and exit openings 18,20 are spaced by the sterilisation chamber 16. The housing 14 is adapted, by virtue of lugs 22 on the outside of an upper surface thereof for attachment to a vehicle such as a trailer 24 (shown in Figures 4 and 5) which in turn can be pulled by a motor vehicle such as a tractor 26. The trailer 24 per se and the tractor 26 are of conventional form and do not constitute part of the present invention. Heating means, in this embodiment in the form of gas burners 28 are provided in the housing 14 for heating the sterilisation chamber 16 to a temperature effect to substantially sterilise the soil 12 passing therethrough. The apparatus 10 is attached to the trailer 24 in a manner so that its height relative to the ground G can be controlled. This is performed in a known way and also does not form part of the present invention. Nevertheless, with the apparatus 10 attached to the trailer 24 which in turn is towed by the tractor 26, the apparatus 10 can be lowered to a position where the entry opening 18 is at a predetermined depth below ground level G so that as the tractor 26 traverses the ground G, the top layer of soil 12 down to that depth enters the housing 14 through the entry opening 18, passes through the sterilisation chamber 16 where it is substantially sterilised by the heat generated by the gas burners 28 and then is returned to the ground G through the exit opening 20.

In more detail, the apparatus 10 is essentially in the form of a rectangular box with open opposite ends, those open opposite ends constituting the entry opening 18 and exit opening 20. The housing has a upper wall 30, and side walls 32 and 34 depending from opposite edges of the upper wall 30. A bottom wall 36 opposite the upper wall 30 is essentially in the form of a replaceable ground cutting blade 38.

The blade 38 has a leading cutting edge 40 for cutting into the ground G and assisting in directing the ground through the entry opening 18 into the sterilisation chamber 16. As shown most clearly in Figure 2, the front edges of the side walls 32 and 34 are also provided with ground engaging blades 42 and 44 respectively to assist in cutting into the ground G to the required depth and directing the top layer of soil 12 into the entry opening 18. Advantageously, the side blades 42 and 44 are also replaceable.

The gas burners 28 are arranged in three stages along the sterilisation chamber 16. The gas burners 28 in each stage comprises a conduit 46 having a first length that extends transversely across and on the inside of the upper wall 28 and opposite second lengths vertically that extend down and on the inside of side walls 32 and 34. Thus, the conduits can be considered to be generally in a shape of an inverted U. As shown in Figures 2 and 3, the length of the conduit 46 along the inside of the upper wall 30 is provided with (four) nozzles 48 from which gas 50 is sprayed into the sterilisation chamber 16. The lengths of the conduit 46 extending on the inside of the side walls 32 and 34 are provided with two nozzles 48 for spraying gas 50 into the sterilisation chamber 16. The conduits 46 are protected from abrasion and other damage caused by the soil 12 flowing through the housing 10 by lengths of right hand angle 52 that effectively encase the conduits 46 with the inside of the walls 30,32,34 of the housing 14. The nozzles 48 extend from the conduit 46 to an opening (not shown) on the right hand angle 52 to deliver the gas 50 into the sterilisation chamber 16.

An air injection system is also provided in the apparatus 10 to assist in the combustion of the gas 50 and also to assist in directing and moving the soil 12 through the housing 14. The air injection system includes a first air conduit 54 extending transversely across the inside of the upper wall 30 adjacent the entry opening 18 and a series of second conduits 56 arranged in stages along the combustion chamber 16. The first conduit 54 is provided with a number of holes (in this case four) for directing compressed air diagonally across the entry opening 18 from the top of the housing 14 to the bottom. This effectively creates a curtain of air 57 that assists in blowing the soil 12 through the sterilisation chamber 16. The conduit 54 is protected from damage by a short length of angle iron 55 attached to the inside of the upper wall 30.

The second air conduits 56 are formed parallel to the space slightly behind the gas conduits 46. The second air conduits 56 have an upper length extending transversely along the inside of the upper wall 30 and provided with four nozzles 58 for providing a spray of air 60 into the sterilisation chamber 16. In this regard, the nozzles 58 extend from the conduit 50 to corresponding holes (not shown) formed in the adjacent length of right hand angle 52. Likewise, lengths of the conduit 56 that extend along the inside of the side walls 32 and 34 each provide two jets of air 60 into the chamber 16. Typically, the air injected through the conduits 56 is at a lower pressure than that provided through conduit 54.

Near the exit opening 20, a water injection system 62 is provided for spraying water typically in the form of a fine mist (Calif ornian type mist) onto the soil 12 prior to it passing out of the housing 14 through the exit opening 20. This assists in extinguishing any combustion of vegetation within the soil 12. The injection of the water has other beneficial effects including reducing the creation of dust and also absorbing smoke which, is effectively returned to the ground via the water spray. This assists in fertilising the soil 12 prior to exiting the apparatus 10. Due to the temperature within the housing 14, the water spray is most likely to turn to steam. In the embodiment shown, the water injection system includes only a single manifold 64 for providing a spray of water 65 near the exit opening 20. However further water spray conduits can be provided inside the housing 14 to further assist in dust suppression and/or temperature regulation. The conduit 64 is protected from abrasion by angle iron 67 fixed to the inside of upper wall 30.

As is most apparent from Figure 1, the front face of the housing 14 was inclined rearwardly from the upper wall 30 to the blade 38. That is, in the direction of travel, the cutting edge 40 of the blade is behind the forward most edge of the upper wall 30. This configuration further assists in insuring that the soil is directed inside the housing 14 rather than over the top of the housing.

In use, referring to Figures 4 and 5, it is envisaged that a plurality of apparatus 10 will be mounted to the trailer 24 in two rows where the apparatus 10 in each row are spaced from each other, and the apparatus 10 in one row are staggered relative to the apparatus 10 in the other row. The apparatuses 10 are mounted in a conventional manner which allows them to be vertically raised and lowered. Such a manner of mounting is commonly used in farming equipment and does not form part of the present invention.

In one embodiment, the apparatus 10 would be 300 mm wide, 225 mm high and 1000 mm long. A preferred operating temperature within the sterilisation chamber 16 is 700°C. In order to provide sufficient time to substantially sterilise the soil, a ground speed of approximately 11 km/h is preferred and a cutting depth, or top soil depth of 40 mm is preferred although it is envisaged that including the top soil to a depth of 20 mm to 40 mm will be sufficient to kill most weeds, insects and bacteria etc that would ordinarily otherwise have an effect on the growing of desired crops. It is envisaged that in use, it may be preferred to have a cultivator and mulcher precede the apparatus 10 either, being drawn by the same vehicle 26 or simply drawn in front of the apparatus 10 in a separate vehicle.

Use of the apparatus 10 replaces the need to spray insecticide/herbicides to control weeds, insects and other pests. Initial projections indicate that the cost of use of the apparatus 10 would be in the order of 20% of the cost of spraying insecticides/herbicides on a per hectare basis.

Now that an embodiment of the invention has been described in detail it will be apparent to those skilled in the relevant arts that numerous modifications and variations may be made without departing from the basic inventive concepts. In the preferred embodiment, the heat for sterilisation is provided by direction injection of a combustible gas into the sterilisation chamber 16. However, other means of generating heat can be used such as use of electric heaters for super heated steam but these are not preferred on the basis of their substantially higher energy requirements and costs of operation. Also, different configurations of gas burners, water and air injection systems can be used.

All such modifications and variations together with others that would be obvious to a person of ordinary skill in the art are deemed to be within the scope of the present invention the nature of which is to be determined from the aforegoing description and the appended claims.

Claims

The Claims Defining the Invention are as Follows:

1. An apparatus for sterilising a top layer of soil including: a housing defining a sterilisation chamber having an entry opening at one end to admit a top layer of soil into the housing and, an exit opening at an opposite end of the housing spaced from the entry opening by the sterilisation chamber, the housing adapted for attachment to a vehicle; and heating means for heating the sterilisation chamber to a temperature effective to substantially sterilise the soil passing through the sterilisation chamber; wherein the apparatus is coupled to a vehicle and lowered to a position where the entry opening is at a predetermined depth beneath the ground level and when the vehicle is operated to traverse the ground, a top layer of soil down to that depth enters the housing through the entry opening, passes through the sterilisation chamber where it is substantially sterilised by heat from the heating means, and returned to the ground through the exit opening.

2. An apparatus according to claim 1 wherein the heating means heats the sterilisation chamber to a temperature in the order of or above 700┬░C.

3. An apparatus according to claim 2 wherein said heating means includes one or more gas burners adapted for burning gas inside the sterilisation chamber.

4. An apparatus according to claim 3 wherein each gas burner comprises a manifold provided with one or more nozzles for spraying gas into the sterilisation chamber.

5. An apparatus according to claim 4 further including a water injection system for spraying water onto the soil traversing the sterilisation chamber prior to passing through the exit opening.

6. An apparatus according to claim 5 further including an air injection system for injecting air into the sterilisation chamber in a general direction from the entry opening to the exit opening to assist in combustion of the gas and directing the soil into and through the sterilisation chamber.

7. An apparatus according to claim 6 further including replaceable ground engaging blades disposed about the entry opening for cutting into the ground and for directing soil into the entry opening.

8. A method for sterilising a top layer of soil including: providing a housing defining a sterilisation chamber and having an entry opening at one end to admit a top layer of soil into the sterilisation chamber and an exit opening at an opposite end spaced from the entry opening by the sterilisation chamber; heating means for heating the sterilisation chamber to a temperature effective to substantially sterilise the soil passing through the sterilisation chamber; coupling the housing to a vehicle; and, operating the vehicle to traverse the ground and simultaneously lowering the apparatus so that the entry opening is at a predetermined level beneath the ground so that the top layer of soil to that depth enters the housing through the entry opening and passes through the sterilisation chamber where it is substantially sterilised by heat, and thereafter returning the sterilised soil to the ground through the exit opening.