FIELD OF THE INVENTION

The present invention relates to a method and plant for decontaminating soil. More particularly, the present invention concerns a mobile and modular soil treatment plant for on site sanitation.

BACKGROUND OF THE INVENTION

There is economic interest in the regeneration of land, particularly in urban areas, after polluting installations such as chemical or petrochemical works have been dismantled and removed. The regeneration releases valuable real-estate for the development of new projects such as sports or entertainment complexes, parks and housing. Polluting installations typically permeate the land with organic contaminants and the inorganic contaminants. The organic contaminants are usually water-insoluble and adsorbed on the surface of mineral grains or solids. The organic contaminants are often concentrated in the fine grain-size fraction of the material (fines i.e. silt and clay). The inorganic contaminants, which include among others: arsenic, copper, mercury, selenium, zinc are found in the soil as metal complexes adsorbed on the surface of minerals grains, mineral phases carrying the contaminants, metals alloys and metallic debris. According to various literature reviews, the inorganic contaminants are also largely confined in the fines.

In the regeneration process, the contaminated soil is excavated, transported to a decontamination facility, where it is processed to remove a contaminated residue that is disposed in carefully regulated landfill sites. The decontamination processes available include physical, chemical and microbiological treatments. Physical treatment methods include flushing contaminants out of the soil using water, chemical solvents or air. Chemical treatment is carried out by addition of chemicals to the soil to render the contaminants harmless or to encapsulate them thus preventing them from spreading. Biological treatment methods include the use of natural organisms to break down the contaminants.

The decontamination process can be carried out off site or on site. A problem with off site decontamination is the requirement to transport soil to the decontamination facility. For large commissions, movement of soil involving road transportation can be highly expensive and slow. In this respect, on site decontamination processes prove a valuable alternative.

One complication with on site decontamination processes is that the decontamination plant has to be such that it is mobile and transportable. In general, such plants are modular and are assembled at the decontamination site. Such installations are described in DE4007703, WO96/30134 and EP0354239.

Disadvantages of known on site decontamination plants include a cumbersome installation procedure, as well as the need for a relatively large site to cover the whole plant and all of its components.

It is, therefore, an object of the present invention to provide an improvement over the prior art.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that this detailed description, while indicating preferred embodiments of the invention, is given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art.

SUMMARY OF THE INVENTION

The present invention relates to a modular and mobile soil treatment plant for decontaminating soil and to a method for decontaminating soil, with the plant according to the invention.

The plant comprises at least means for holding soil and means for holding soil treatment agents. Optionally, means for holding a liquid are also provided. The liquid can be water or any other liquid which is needed in the decontamination process. Soil and treatment agents (and optionally liquid) can be dispensed from their respective holding means into a means for mixing and/or treating the soil, the treatment agents and optionally the liquid. The means for mixing and/or treating can be connected to the soil, treatment agents and optionally liquid holding means via tubings. The mixed/treated substance (i.e. soil, treatment agent and optionally liquid) can be discharged from the means for mixing and/or treating onto means for discharging the mixed/treated substance from the plant.

All the components (i.e. the means for holding soil, treatment agents and optionally liquid, as well as the means for mixing and/or treating and the means for discharging the mixed/treated substance from the plant) are housed or arranged in cuboid open frames.

The plant comprises minimum two such frames. The frames are characterized in that they can be stacked vertically and can be interlocked or dismounted according to the needs. In this way, all the components are in close proximity to each other. In addition, the stacked frames can be displaced horizontally with regard to each other.

As such, the invention provides for a compact installation or plant with a generally vertical arrangement, thereby reducing the need for extensive space requirements to install the plant. Each frame housing one or more components of the plant can be considered as a separate module of the plant.

In a preferred embodiment, the frames housing the various components have the dimensions of a shipping container. Such containers have standard sizes, thereby facilitating transport of the plant when dismounted into its individual modules or frames (e.g. shipment overseas or transport by train).

In a preferred embodiment, the plant comprises three frames or modules. A first frame comprises the means for holding soils, the means for holding treatment agents and optionally the means for holding liquid. This first frame is stacked vertically above a second frame, which comprises the means for mixing and/or treating the soil, treatment agents and optionally the liquid. The second frame in its turn is stacked vertically above a third frame, which comprises the means for discharging the mixture of soil, treatment agents and optionally liquid from the plant.

It will be clear for a person skilled in the art that alternative arrangements fall within the scope of the present invention (e.g. the various holding means can be provided in separate frames, or a multitude of holding and/or mixing/treatment means can be provided in one or more frames). Additional components can also be added in existing frames or additional frames, according to the specific needs (e.g. means for filtering, dewatering etc).

In a preferred embodiment, the means for holding soil and the means for holding treatment agents are hoppers, of which the size can be adapted according to the specific commission. These hoppers can be connected via a basal sump and tubings to the means for mixing and/or treating. These means for mixing and/or treating are preferable one or more revolving drums. Alternatively, the means for mixing and/or treating can comprise augers or vibrating elements. In general the means for mixing and/or treating comprise a device for agitating the introduced components. The mixed/treated substance is loaded onto means for discharging or exporting from the plant, which comprises preferable one or more conveyor belts. This conveyer belt preferentially protrudes through and extends from the frame wherein it is housed, and inclines outwardly.

In a preferred embodiment, the individual frames can be horizontally displaced with regard to each other. Preferentially, the most basal frame (i.e. the frame comprising the means for discharging the mixed/treated substance from the plant) is displaced horizontally with regard to the frame which is vertically stacked above. Such an arrangement allows for a much steeper inclination of the means for discharging (i.e. the conveyor belt), as the conveyor belt can protrude through the top of the frame, which is partially freed due to the horizontal displacement of the frame stacked vertically above. As a consequence, a conveyor belt of a given length reaches a higher altitude, and more soil can be deposited in one batch, leading to less shut down time of the plant to remove the treated or decontaminated soil or mixture. In addition, the decontaminated soil or mixture can be deposited relatively close to the plant. An arrangement without the horizontal displacement of the frames would necessitate either the use of multiple conveyor belts or longer conveyor belts to reach the same height. Moreover, the distance from the plant would be greater, necessitating more available space on site.

In addition to the components described above, in a preferred embodiment, the plant also comprises walking bridges along one or more sides of the exterior of one or more frames. These walking bridges can be foldable fixed to the respective frames or alternatively can be attached during the on site assembly of the plant. Inside one or more frames, operator platforms are provided. These walking bridges and operator platforms ensure easy access throughout the plant.

The present invention also relates to a method for decontaminating soil with the soil treatment plant according to the invention, wherein soil, treatment agents and optionally liquid are loaded in their respective holding means, from which these are dispensed in the means for mixing and/or treating, after which mixing/treating the mixed substance is exported from the plant via the means for discharging.

DESCRIPTION OF FIGURES

Figure 1 illustrates schematically the components and their arrangement of a soil treatment plant according to a preferred embodiment of the present invention.

Figure 2 illustrates a perspective view of a stackable frame according to a preferred embodiment of the present invention. Figure 3 illustrates a front view of a soil treatment plant according to a preferred embodiment of the present invention.

Figure 4 illustrates a side view of a soil treatment plant according to a preferred embodiment of the present invention.

Figure 5 illustrates a top view of a soil treatment plant according to a preferred embodiment of the present invention.

Figure 6 illustrates a top view of horizontally displaced, vertically stacked frames according to different embodiments of the present invention.

Figure 7 illustrates a front view of the small rectangular 31 end of the frame in upright position (left panel) for transport and rotated (right panel) for assembly.

DETAILED DESCRIPTION

A preferred embodiment of the invention is illustrated with reference to the figures.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art. All publications referenced herein are incorporated by reference thereto.

The articles "a" and "an" are used herein to refer to one or to more than one, i.e. to at least one of the grammatical object of the article. By way of example, "an inlet" means one inlet or more than one inlet.

Throughout this application, the term "about" is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of inlets, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0).

The present invention relates to a mobile soil treatment plant 1 for decontamination of soil containing organic and inorganic contaminants. The inorganic contaminants includes both radioactive and non-radioactive metals, and is otherwise intended to encompass the full breadth of metal contaminants known to those skilled in the art; in particular for example as used herein, the terminology "inorganic contaminants" is meant to include or refer to

Pb, Cu and Zn. Organic contaminants refers to all organic compounds which tend to adhere to soil, and which may present environmental hazards when permitted to remain in the soil; in particular for example as used herein, the terminology "organic contaminants" is meant to include or refer to C10-C50 petroleum hydrocarbons (i.e. hydrocarbon materials containing from 10 to 50 carbon atoms).

The process of the invention is based on the steps of adding soil, treatment agents and optionally liquid, mixing these components and discharging the mixed substance from the plant 1.

The soil of the invention is understood to mean superficial earth crust, whether natural or man made (consolidated or unconsolidated mantle), namely aggregate material including but not limited to aggregate material disposed on dry land masses (e.g. soil aggregate material); sedimentary aggregate including any bottom sediments of fresh or marine water systems; aggregate material which comprises organic material derived for example from plant or animal sources; organic material such as plant material would usually form part of the courser aggregate material as described hereinafter and would include, for example, tree stumps, ligneous particles, etc.; aggregate material derived from human activities, such as, for example, mineral aggregate materials, fill aggregate materials as well as sediments arising in water-ways; mineral aggregate residues from mining operations, such as those present in a tailings pond; etc. Thus soil includes all forms of particulate matter, such as, for example, clay, fines, sand, stones, rock organic material, etc.

In an embodiment of the invention, the soil to be decontaminated can be pretreated before being subject to the method of the invention. Such pretreatment can include one or more of the following steps: removing objects of greater than 5 cm in size from the soil using for instance one or more screens, removing ferrous objects from the soil using magnetism, using a vibrating screen to separate out gravel from the soil, leaving the remainder of the soil comprising sand, silt and clay. In the alternative, one or more of the aforementioned steps can be included in the method of the present invention.

In a preferred embodiment, before the contaminated soil enters the means for mixing and/or treating, it is screened to remove large objects greater than a nominal size of 40 mm, 50 mm, 60 mm, 70 mm or 80 mm, which objects include stones, cobbles, bricks, etc that would otherwise damage to the plant from larger cobbles, bricks, etc. This may be carried out using any suitable technique of the art, including an apertured mesh, disposed with a plurality of apertures of suitable size to screen out undesired objects. The (screened) contaminated soil 10 is fed to means for holding soil 5. It may be fed using any suitable means, for example, by a crane or wheel-loader or directly via a conveyor belt from the pre-screening stage. These means for holding soil 5 can be a hopper, or any type of container or tank provided with a basal sump and/or valves.

Treatment agents 11 are provided in treatment agent holding means 6. These means can likewise be a hopper, or any type of container or tank provided with a basal sump and/or valves. If needed more than one treatment agent holding means 6 can be provided, in the case multiple treatment agents 11 need to be applied, or alternatively, multiple treatment agents 11 can be premixed in one treatment agent holding means 6. These treatment agents 11 comprise all known chemical and/or microbiological treatment agents known in the art. A person skilled in the art will appreciate that according to the type of treatment agent 11 , a specific type of holding means 7 may be necessitated.

Optionally, if needed, liquid 12 can be provided in liquid holding means 7. Such liquid holding means 7 can be any kind of container or tank provided with a basal sump and/or valves. In the alternative, liquid 12 may be provided from an external (i.e. not comprised in the plant 1 ) source, such as a reservoir, a well etc via tubings, pipes or the like. The liquid 12 can be water, a watery solution, or any other liquid required in the soil treatment process, depending of the composition of the soil, the composition of the contaminants and/or the specific treatment agents and their solubility in water or any other liquid. If needed, the treatment agents 11 can be premixed with the liquid 12 to create a solution or a suspension.

The soil 10, treatment agent 11 and optionally liquid 12 are fed from their respective holding means 5, 6, 7 to means for mixing and/or treating 8, through gravity and/or mechanically aided (e.g. with pumps or augers), whereby the respective holding means 5, 6, 7 are proximal to or in close proximity of the means for mixing and/or treating 8. The respective holding means 5, 6, 7 are connected to the means for mixing and/or treating 8 preferentially via tubings. Alternatively, soil 10 and/or treatment agents 11 can be delivered to the means for mixing and/or treating 8 for instance via conveyor belts or augers. The means for mixing and/or treating 8 comprises preferentially one drum with one or more rotating axles with mixing paddles and blades. Such means operate in a similar manner as for instance a cement mixer or the like. In the alternative or in addition hereto, the means for mixing and/or treating 8 can comprise vibrating means and/or augers. If needed, a multitude and/or a combination of means for mixing and/or treating 8 can be provided in series (i.e. provided sequentially) or in parallel (i.e. provided as independent means).

The mixed soil, treatment agent and optionally liquid 13 is subsequently fed to or deposited on means for discharging 9 this mixture from the plant 1 , through gravity and/or mechanically aided means (e.g. with pumps or augers), whereby the discharging means 9 are proximal to or in close proximity of the means for mixing and/or treating 8. The discharging means 9 is preferentially a conveyor belt of any type for the displacement of soil known to a person skilled in the art. In the alternative, an auger may be used for discharging 14 the mixture from the plant 1.

Optionally, if liquid 12 has been added in the soil treatment process, additional means can be provided for partially or completely removing or draining the liquid prior to discharging 14 the mixture from the plant 1. Such means may comprise for instance dewatering screens or cyclones.

Another aspect of the invention concerns a mobile soil washing plant 1 configured to carry out the method of the invention.

One embodiment of the invention is a mobile soil treatment plant 1 comprising the components as describe above, wherein one or more of the components is housed within an open frame having a cuboid shape. The component in question may be the soil holding means 5, treatment holding means 6, liquid holding means 7, mixing/treatment means 8, and discharging means 9. Preferably, each of the aforementioned components is house within a cuboid frame. The component is attached to the frame using any means, for example, using bolts, nuts and bolts, by welding or riveting.

Preferably, the cuboid frame comprises a supporting beam along each edge of the cuboid e.g. at least 12 supporting beams, one along each edge of the cuboid. The edge beams are joined at the cuboid apices. One or more faces of the cuboid may be disposed with a cross beam which connects opposing apices, opposing edges, or an edge to an opposing apex. The number of cross beams in the cuboid frame may be 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, or 20. A cross beam may be diagonal or parallel to an edge of the cuboid. The number of diagonal cross beams in the cuboid frame may be 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20. The frame serves to support the machinery, facilitate dismountable stackability, the open frame allowing convenient and full access to all sides. To further facilitate stacking one or more of the frame apices or edges may be disposed with a locating means configured to couple with corresponding locating means on another frame. The locating means allows a frame to dismountably stack within a given tolerance, vertically on top of another frame, preventing misalignment and sideways displacement. The locating means can be any in the art, for instance an upper and lower surface co-operating rim, or a protrusion-groove arrangement, whereby a protrusion in base of one frame is configured to couple with a groove in the top of another frame (or vice versa). Because the locating means prevents misalignment, the possibility becomes available to stack 2, 3, 4, 5, 6, 7, 8, 9 or 10 frames vertically.

An example of a cuboid frame 18 is shown in Figure 2 which depicts the frame formed from four longitudinal supporting beams 19, 20, 21 , 22 of equal length, which comprise the four long edges of the cuboid frame 18, and eight shorter (end) supporting beams 23, 24, 25, 26, 27, 28, 29, 30 arranged as two end small rectangles (23, 24, 27, 28, and 25, 26, 29, 30) which constitute the small rectangular ends 31 , 32 of the cuboid frame. Each of the longitudinal supporting beams 19, 20, 21 , 22 is attached at either end to a corner 47, 48, 49, 50, 51 , 52, 53, 54 of the aforementioned small rectangular ends 31 , 32 so giving rise to the cuboid shape of the frame. The frame is also disposed with a plurality of diagonal cross beams, connecting a corner to a longitudinal supporting beam e.g. 33, 34, 35, 36 or a corner to an end supporting beam e.g. 37, 38, 39, 40 or connecting one longitudinal supporting beam to an adjacent longitudinal supporting beam e.g. 41. The frame is also disposed with a plurality of parallel cross beams, that are disposed parallel to the frame edges and connect adjacent longitudinal supporting beams e.g. 42, 43, 44, 45, 46. The frame corners 47, 48, 49, 50, 51 , 52, 53, 54 are provided with means to facilitate stackability e.g. a protrusion and receiving aperture, or means for interlocking stacked frames e.g. perforations of the beams whereby opposing beams of stacked frames can be interlocked, fixed or held together using bolts, nuts and bolts or the like. Similar protrusions and receiving aperture or means for interlocking stacked frames 55, 56, 57, 58, 59, 60, 61 , 62 are provided on each of the longitudinal supporting beams 19, 20, 21 , 22. These protrusions and receiving aperture 55, 56, 57, 58, 59, 60, 61 , 62 allow interlocking of vertically stacked and horizontally displaced frames.

The interlocking means 47-62 are arranged such that a multitude of vertically stacked configurations of the cuboid frames 18 can be obtained. The number of interlocking means per cuboid frame 18 is preferentially between 8 and 40, and can depend on the preferred configuration. Figure 6 illustrates embodiments of the present invention whereby the vertically stacked cuboid frames 18 are mutually horizontally displaced. Various configurations are illustrated with two vertically stacked cuboid frames 2, 3. The top panel illustrates a horizontal displacement 16 along the longitudinal axis of the frames. The middle panel illustrates a horizontal displacement 70 perpendicular to the longitudinal axis of the frames. The bottom panel illustrates a horizontal displacement whereby the frames are rotated 71 with regard to each other. It will be clear that, depending on the specific needs, combinations of the various configurations can be realized with a multitude of frames.

The size of the frame preferably corresponds to that of a shipping container, thereby allowing convenient transportation using a shipping vessel, crane, railway and truck, and further permitting vertical stacking. The skilled person will be aware of the standard shipping container sizes. The three most common types of shipping container have their dimensions expressed in imperial units. The twenty foot container has external dimensions length 20' 0" (6.096 m) x width 8' 0" (2.438 m) x height 8' 6" (2.591 m); the forty foot container has external dimensions length 40' 0" (12.192 m) x width 8' 0" (2.438 m) x height 8' 6" (2.591 m) and the forty-five foot high-cube container has external dimensions length 45' 0" (13.716 m) x width 8' 0" (2.438 m) x height 9' 6" (2.896 m).

The orientation of the individual cuboid frames 18 during transport of the plant can be different from the orientation of the frames in the assembled plant 1 , i.e. the frames 18 can be tilted or rotated 69 90° along their central longitudinal axis, as illustrated in Figure 7. The standard container which is suitable for housing the components or modules of the plant according to the invention usually has a standard width 72 (usually 8' 0") which is smaller than the standard height 73 (usually 8' 6" or 9' 6"). The possibility to rotate or tilt 69 the container 18 allows slightly wider components (e.g. the means for mixing 8) to still fit within a container with standard dimensions. It will be clear that the placement, arrangement or configuration of the supporting beams and/or cross beams may be altered in a cuboid frame 18 which is rotated 69 in an assembled soil treatment plant 1.

In a preferred embodiment of the invention, the soil treatment plant 1 comprises two or more frames 18, preferentially three frames 18 dismountably stacked vertically and interlocked, in which the above described components are housed. A first frame 4 comprises the holding means for soil 5, the holding means for treatment agents 6 and optionally the holding means for liquid 7. This first frame is stacked vertically above a second frame 3, which second frame 3 comprises the means for mixing and/or treating 8. As such, the components housed in the first frame 4 are in close proximity of the components housed in the second frame 3 (i.e. vertically arranged). This second frame 3 is stacked vertically above a third frame 2, which third frame 2 comprises the means for discharging 9 the mixed/treated substance 13 (i.e. soil, treatment agent and optionally liquid). As such, the components housed in the second frame 3 are in close proximity of the components housed in the third frame 2 (i.e. vertically arranged).

Preferentially, one or more of the frames 2, 3, 4 comprise an operator platform, allowing easy access to the components and control units housed within the respective frame. Access to the operator platform is provided via ladders 67, stairs or the like which can be prefixed to the respective frame or attached on site. Preferentially one or more frames 2,

3, 4, are provided with walking bridges 63, 64, 65, 66 along the exterior of the frame 2, 3,

4, preferentially along the long edges of the frame 2, 3, 4, likewise allowing easy access. Such walking bridges 63, 64, 65, 66 can be attached to the frame 2, 3, 4 on site or can be prefixed to the frame. Preferentially, the walking bridges 63, 64, 65, 66 are hinged to the frame and can be folded in.

Also in a preferred embodiment, the vertically stacked frames 2, 3, 4 can be displaced horizontally 15, 16 along the long edges 19, 20, 21 , 22 of the frame 18 relatively to each other, whereby the frames can be interlocked with one or more pairs of opposing interlocking means 47-48, 49-50, 55-57, or 56-58 on one frame and one or more pairs of opposing interlocking means 51-52, 53-54, 59-61 , or 60-62 on a vertically above positioned frame. It will be clear to a person skilled in the art that the exact position and amount of interlocking means may vary within the scope of the present invention.

Further in a preferred embodiment, the means for discharging 9 the mixed/treated substance 13 protrude through and extend from the frame 2 wherein it is housed with an variable outward inclination 17 (i.e. the end of the discharging means 9 extending from the frame 2 is elevated relative to the end of the discharging means 9 confined within the frame 2). Such an arrangement allows the deposit of mixed/treated substance 14 adjacent to the plant as an elevated mass or pile 68. A configuration of the plant 1 as depicted in Figure 1 , whereby the frame 3 vertically stacked above the frame 2 housing the discharging means 9 is displaced horizontally over a given distance 16, relative to the frame 2 housing the discharging means 9, frees or opens up a top section of the frame 2, bordered by a section of beams 19 and 20 as well as beam 28 or 30 of frame 2 and further bordered by beam 27 or 29 of the frame 3 vertically stacked above, which section is equal in length to the amount of displacement 16. Such an opening allows for the discharging means 9 to protrude through and extend from the top side of the frame 2 through the opened section. In this way, discharging means 9 of a given length can reach a higher altitude, due to an increased inclination, thereby being able to continuously (i.e. uninterrupted) discharge 14 and deposit more mixed/treated substance 68. To reach the same altitude with a lower inclination (i.e. the discharging means 9 protruding through and extending from the frame 2 via the rectangular ends 31 or 32), the discharging means 9 would have to be either longer or additional transporting means with a higher inclination would have to be provided at the exterior of the plant 1 , in either case requiring additional space on the decontamination site.