WO2008061320A1

WO2008061320A1 - Classification apparatus and method

Info

Publication number: WO2008061320A1
Application number: PCT/AU2007/001809
Authority: WO
Inventors: Lindsay Edward Bone
Original assignee: Lindsay Edward Bone
Priority date: 2006-11-23
Filing date: 2007-11-23
Publication date: 2008-05-29

Abstract

A classification apparatus including a fluid container holding an amount of fluid, a sample vessel for holding a sample amount of material to be classified, with a lower portion of the sample vessel in fluid communication with the fluid in the fluid container; and an agitating mechanism to move the sample material relative to the fluid in the fluid container to agitate the sample material.

Description

CLASSIFICATION APPARATUS AND METHOD Field of the Invention.

The present invention relates to classification apparatus and method of operation and particularly to density separation for material testing. Background Art.

In commercial operations, coal quality can be "upgraded" by taking advantage of the relationship between particle ash (more correctly termed inherent mineral matter) percentage and particle relative density. Upgrading in a Coal Handling Preparation Plant (CHPP) is ascertained by density separations. The density separations are commonly performed using dense media, cyclones, spirals or jigs.

The standard laboratory test method is the "float and sink" test where a series of different density liquids are used to effect separation of the coal sample into a series of discrete density fractions. By measuring the mass and ash of these discrete fractions it is possible to establish information about a coal sample that can be used to:

> Assess resource potential;

> Predict results of simulated plant operations; y Design commercial coal preparation plant; and

> Examine products from the CHPP for routine control purposes to assess separation efficiency.

The use of halogenated hydrocarbon liquids to achieve the high relative densities required for float and sink testing has long been recognized as a health and environmental safety issue. The basic acceptance of the float and sink test came about because of the drawbacks associated with the equipment first used for classification. The early equipment was based on manual "jigging" of the sample.

One example of an early device which was replaced by the float and sink test, is termed a "Henry Tube". A Henry tube As illustrated in Figure 1, consists of a generally metal tube with a shallow tray mounted about the upper edge for the convenience of removing samples. The tube is partially submerged in a water bath, normally a tube of larger diameter than the Henry tube. Handles are fixed slightly below the tray for convenience in jigging the tube in and out of the water bath. Approximately 25 mm above the bottom of the tube, a brass collar is provided about the interior of the tube serving as a support for a brass disc pierced with holes and upon which rests a wire gauze.

The water bath is substantially filled with water and the jig tube is lowered into it. A suitable quantity of coal or other material to be tested is placed in the tube after weighing the material. The tube is then jigged up and down in the water bath for about 1 minute. It is normally advised that the downward stroke be made forcefully and the upstroke should be slow.

This separates the particles of coal due to settling and their relative settling velocities which is related to particle specific gravity. The clean coal which has a lower specific gravity works upwardly toward the top of the column and the heavier material is concentrated at the bottom of the tube.

The time of jigging and the number of strokes should be standardized, because if not the results on different samples of coal will not be comparable. Also, by adhering to a definite routine, the personal element is reduced to a minimum.

When complete, the jig tube is removed from the water bath and allowed to drain, and the column of coal is pushed cautiously upwards by means of a wooden rod. When a plug of coal of approximately 10 to 15 mm in height protrudes from the top of the tube, it is carefully scraped via the tray into a weighed basin and the rest of the contents are removed similarly. Each layer is dried, weighed, finely ground and the ash content is determined. The data can then be used to plot a "washability curve" of cumulative mass of the sample versus cumulative ash %.

The Henry tube then developed into a further test apparatus as illustrated in Figure 2. This apparatus has a pair of chambers containing a fluid, in fluid communication with each other via a lower channel. The coal sample is place in one of the chambers again in a sample tube with a gauze, screen or similar located at the bottom end. The second of the chambers is provided with a piston connected to a manual crank. Rotation of the crank forces the piston downwardly in the chamber, which in turn forces a fluid "pulse" through the lower channel and upwardly through the sample tube.

Both of the above apparatus are largely limited by the need to be manually operated. This manual operation leads to variability in the collected results, which is to be avoided in order to produce useable results. The float and sink test has therefore become the industry standard test even though it uses halogenated hydrocarbon liquids or other chemical solutions such as metapolytungstates, zinc- chloride solutions or hematite suspensions which have significant associated health and environmental safety issues.

Therefore, it would be a significant advance to the art if a simple testing apparatus was developed which overcame the health and environmental safety issues of the float and sink test and also allowed collection of reliable results.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

Summary of the Invention. The present invention is directed to a classification apparatus and method, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice. hi one form, the invention resides in a classification apparatus including i. a fluid container holding an amount of fluid, ii. a sample vessel for holding a sample amount of material to be classified, with a lower portion of the sample vessel in fluid communication with the fluid in the fluid container; and iii. an agitating mechanism to move the sample material relative to the fluid in the fluid container to agitate the sample material.

In a second form, the invention resides in a method for classifying particulate material according to specific gravity, the method including the steps of i. providing a jigging apparatus including a fluid container holding an amount of fluid, a sample vessel for holding a sample amount of material to be classified, with a lower portion of the sample vessel in fluid communication with the fluid in the fluid container; and an agitating mechanism to move the sample material relative to the fluid in the fluid container; ii. agitating the sample vessel for an optimum time period, t, and at an optimum fluid velocity of the fluid into the sample vessel. Whilst the present invention was invented with a particular application in the mind of the inventor, namely the classification of coal, the apparatus and method can be used to assay any particulate material and particularly mineral sands, iron ores, and gem bearing gravels. The present invention is described herein with particular reference to classification of coal particles.

The present invention will preferably utilise a mechanical pulsation of sample of particulate material in a fluid, typically water, to sort the particles into a density continuum whence a separation into density ranges is physically simple.

For coal particulate, subsequent mass/ash/density measurements can be made and that data can be used to generate yield/ash curves in a manner equivalent to conventional flat/sink test data.

The mechanical pulsation is a cyclical process involving bed expansion and segregation through the pulsation of the particle bed by a current of water. A jig cycle is generally composed of two main stages, namely fluidisation and sedimentation. The upstroke of the sample vessel may be the start of the cycle. At the end of the lift stroke, the sample vessel and the bed fall through the liquid in the liquid container. As the sample vessel falls, the relative incompressibility of the liquid fluidises the sample bed (suspend solid particle on on the relatively upward flowing liquid) which results in loosening or expansion of the bed. As the upstroke begins, the bed is drawn upwardly through the liquid resulting in sedimentation of the particles in the sample bed. The cycle is generally repeated for a standardised time period. The rate of sedimentation is affected by the density of the particles in the bed and hence the sample is classified or fractionated according to density of the particles.

The present invention has two basic operational strokes, namely an upstroke which effects fluidisation of the sample bed and a downstroke which has a sedimentation effect on the fluidised sample bed.

The classification apparatus of the present invention will normally be operated in a vertical direction to take advantage of the effects of gravity on the sedimentation of the sample.

The apparatus is provided as an alternative water-based method and apparatus for fractionation of a sample of particulate material based on particle density for a rapid, accurate and safer alternative to using heavy liquids in float sink testing. The apparatus will normally be provided as a mechanical agitation or jigging apparatus. The provision of a mechanical agitation mechanism results in repeatable jigging for more accurate and reproducible testing conditions.

The apparatus includes a fluid container holding an amount of fluid. The fluid used will normally be water but it is envisaged that other fluids could be used in the apparatus with some relatively minor alterations and without deviating from the inventive principle. One such alternative fluid that could be used is air whether compressed or not.

The fluid will typically be provided as a static body in a closed vessel such as a water bath or similar. This may differ when different fluids are provided.

For example, when air is used as the fluid, the air may be injected or blown upwardly into the sample bed. Preferably, when used, the air will be injected in intermittent bursts or pulses to allow for sedimentation time and effect.

Generally, the fluid container will be an elongate hollow vessel. The preferred shape of the fluid container for its simplest embodiment is cylindrical with an open top to contain the body of water. The fluid vessel will preferably be an outer vessel into which the sample vessel will at least partially extend.

Ih circumstances where water is used as the fluid, the water level in the fluid container will preferably not be sufficiently high to completely immerse the sample vessel, even when the sample vessel is at its lowest portion of the downstroke.

The fluid container may be manufactured of any material suitable for the purpose but will usually be plastic or light metal.

The apparatus of the present invention also includes a sample vessel for holding a sample. The sample vessel is also generally an elongate, hollow vessel similar in shape to the fluid container, that is cylindrical with an open top. The sample vessel will normally be located at least partially inside the fluid container.

The sample vessel will normally have a lower portion through which fluid can flow but suitable to prevent egress or loss of particulate from the sample through the lower portion. The portion may therefore be provided as the base wall of the cylindrical container. Typically the base wall will be provided with at least a portion of screen material or sieve-like material such as wire mesh or similar. Preferably, at least a portion of the lower end of the container and most usually, the wire mesh base wall, will be removable in order to harvest the fractions of the sample after jigging the sample is complete.

The sample vessel of the apparatus is typically associated with the agitation means. Most preferably, the sample vessel will be suspended from the agitation mechanism into the fluid container and the fluid therein. It is preferred that the sample vessel is removable from the agitation means in order that it can be removed from the apparatus and attached to a sample fraction retrieval apparatus, a form of which is described below. The inner container (sample vessel) will normally be sized relative to the outer fluid container and there will normally be an optimum size relationship between the diameters of the two containers. The inner sample vessel will also be substantially taller than the height of the sample which it contains in order to have excess height to allow for expansion of the sample bed during the fluidisation stage of the operation.

The apparatus of the present invention also includes an agitating mechanism to move the sample material relative to the fluid in the fluid container to agitate the sample. The preferred agitation mechanism is one which agitates/fluidises the sample periodically as opposed to constantly. This will give the fluidised sample time to settle.

According to a particularly preferred embodiment, the agitation mechanism will preferably agitate the sample in a reciprocating motion. Most preferred is that the agitation mechanism acts to move the sample vessel upwardly and downwardly. The sample vessel will suitably be lifted by the agitation mechanism and then allowed to fall under the force of gravity. The amplitude of the lift or the height to which the sample vessel is raised will also preferably be alterable.

Typically, the agitation mechanism will be associated with at least one attachment arms to attach the sample vessel to the agitation mechanism. Normally there will be more than one attachment arm to balance the load and the sample vessel during movement and each of the arms is normally connected to a lower end of an agitation shaft which extends substantially vertically from the agitation mechanism. The upper end of the agitation shaft will normally be associated with a cam means which through its association with the shaft, is adapted to lift and drop the sample vessel in a cyclical manner.

As stated above, the height to which the sample vessel is lifted during the upstroke is adjustable and is preferably adjusted by providing a different sized cam. The agitation action can also be adjusted by providing a shaped cam. The height from which the sample vessel is dropped will typically affect the fluid velocity through the sample vessel and the sample bed. The height is preferably optimised to give a optimal fluid velocity as a fluid velocity which is too high can result in mixing of the sample rather than classification. The cam will preferably be a substantially semi-circular cam plate mounted for rotation about a horizontally oriented pivot towards one of the corners of the cam. The cam plate may therefore be oriented in a substantially vertical plane. The upper end of the agitating shaft will suitably be provided with an engagement member (normally substantially horizontally oriented) which may be attached to the cam adjacent the other of the corners or the engagement member may simply slide over the edge of the cam plate to be lifted and dropped. A cam size of approximately 150mm is preferred. A larger cam gives results which match the results from the now- popular float/sink test.

The cam plate will normally be rotated by a motor or similar. Further, the rotation speed of the cam means can be altered to adjust the cycle rate of the sample vessel, to an optimum cycle rate in cycles per second. A preferred cycle rate is 1 cycle per second but higher cycles may be used.

There is also a preferred total jigging time. It is preferred that a jigging time of at least 3600 cycles (approximately 1 hour at the 1 cycle per second rate) or at least 1 hour be used. Depending upon the sample makeup, longer jigging times may be used. A tracer means may be used to establish whether the sorting is complete or not.

Once the jigging has been completed, the sample vessel is typically removed from the agitating mechanism and allowed to drain. The sample vessel may be suspended in a sample collection apparatus, typically including clamp means to hold the sample vessel a predetermined distance normally approximately 25 mm) above a tray or similar to allow the removal of the particulate fractions according to their (generally visible) sorted sample horizons. The screen material is generally removed from the base of the sample vessel allowing the sample bed to move downwardly through the sample vessel. A scraping means is used to separate a predetermined height of sample away from the bed. As samples are collected, they are typically separated into drying trays. This step is repeated until a number of samples are collected. Normally at least 8 samples will be required to generate coherent data for assessment.

The collected and separated fractions are then typically dried and the dry mass of the fractions is recorded. The dried fractions are then milled for analysis and the ash% of each fraction calculated. The results can then be used to generate a washability curve as illustrated in Figure 6 for example.

Brief Description of the Drawings.

Various embodiments of the invention will be described with reference to the following drawings, in which:

Figure 1 is a sectional side view of a prior art Henry Tube apparatus. Figure 2 includes a side and sectional front elevation views of a prior art two chamber test apparatus.

Figure 3 is a schematic representation of a preferred embodiment of the present invention.

Figure 4 is a schematic representation of a sample fraction retrieval stand according to preferred embodiment of the present invention.

Figure 5 is a schematic illustration of the movement of the sample material in the down stroke and the up stroke of the preferred embodiment.

Figure 6 is a washability curve of cumulative mass versus cumulative ash % plotted from the data contained in Table 1. Figure 7 is comparison of float-sink and the present apparatus for a)

100 mm cam, b) 150 mm cam, c) 180 mm cam, and d) as a function of the total number of cycles for the optimal process conditions.

Figure 8 is a comparison of washability data(Yield vs Ash%) for a variety of methods. Detailed Description of the Preferred Embodiment.

According to the a preferred embodiment of the present invention, a classification apparatus and method is provided. The classification apparatus 10 illustrated schematically in Figure 3 includes a fluid container 11 holding an amount of water, a sample vessel 12 for holding a sample amount of material to be classified 13, with a lower portion of the sample vessel 12 in fluid communication with the water in the fluid container 11, and an agitating mechanism to move the sample material 13 relative to the water in the fluid container 11 to agitate the sample material. The apparatus will be commonly referred to as a jig.

The agitation mechanism applies mechanical pulsation to the sample bed which is a cyclical process involving bed expansion ad segregation through the pulsation of the particle bed by a current of water. A jig cycle is composed of two main stages, namely fluidisation and sedimentation, with the upstroke of the sample vessel being the start of the cycle. The two main stages are illustrated with the fluid movement through the sample bed in Figure 5. At the end of the lift stroke, the sample vessel and the bed fall through the liquid in the liquid container. As the sample vessel falls, the relative incompressibility of the liquid fluidises the sample bed (suspend solid particle on on the relatively upward flowing liquid) which results in loosening or expansion of the bed. As the upstroke begins, the bed is drawn upwardly through the liquid resulting in sedimentation of the particles in the sample bed. The cycle is generally repeated for a standardised time period. The rate of sedimentation is affected by the density of the particles in the bed and hence the sample is classified or fractionated according to density of the particles.

The jig of the illustrated embodiment is operated in a vertical direction to take advantage of the effects of gravity on the sedimentation of the sample.

The apparatus includes a fluid container 11 holding an amount of water. The water is provided as a static body in a closed vessel such as a water bath. The fluid container 11 is an elongate hollow vessel which is cylindrical with an open top to contain the body of water. The fluid container 11 is an outer vessel into which the sample vessel 12 extends. The water level 14 in the fluid container 11 is not sufficiently high to completely immerse the sample vessel 12, even when the sample vessel 12 is at its lowest portion of the downstroke.

The fluid container 11 is manufactured of any material suitable for the purpose but will usually be plastic or light metal. The apparatus of the present invention also includes a sample vessel 12 for holding a sample 13. The sample vessel 12 is also an elongate, hollow vessel similar in shape to the fluid container, that is cylindrical with an open top.

The sample vessel 12 has a base wall of screen material 15 or sieve-like material such as wire mesh through which fluid can flow but preventing egress or loss of particulate from the sample 13 through the base wall 15. The wire mesh base wall

15 is removable in order to harvest the fractions of the sample after jigging the sample is complete.

The sample vessel 12 of the apparatus 10 is suspended from the agitation mechanism into the fluid container 11 and the water therein. The sample vessel 12 is removable from the agitation means in order that it can be removed from the apparatus 10 and attached to a sample fraction retrieval apparatus (illustrated in

Figure 4), as described below.

According to the illustrated embodiment, the agitation mechanism agitates the sample in a reciprocating motion by moving the sample vessel 12 upwardly and downwardly. The sample vessel 12 is lifted by the agitation mechanism and then allowed to fall under the force of gravity.

The agitation mechanism is associated with attachment arms 16 to attach the sample vessel 12 to the agitation mechanism and each of the arms 16 is connected to a lower end of an agitation shaft 17 which extends substantially vertically. The upper end of the agitation shaft 17 is associated with a cam 18 which through its association with the shaft 17, is adapted to lift and drop the sample vessel 12 in a cyclical manner.

The cam 18 is a substantially semi-circular cam plate oriented in a substantially vertical plane and mounted for rotation about a horizontally oriented pivot 19 towards one of the corners of the cam 18. The upper end of the agitating shaft 17 is provided with an engagement member 20 (normally substantially horizontally oriented) which slides over the edge of the cam 18 to be lifted and dropped. The cam plate is rotated by a motor. Once the jigging has been completed, the sample vessel 12 is removed from the apparatus and allowed to drain. The sample vessel 12 is suspended in a sample collection apparatus, typically including clamp means 21 to hold the sample vessel 12 a predetermined distance, normally approximately 25 mm, above rubber mat 22. A tray 23 or similar is provided to allow the removal of the particulate fractions according to their (generally visible) sorted sample horizons.

The screen base wall 15 is removed from the sample vessel 12 allowing the sample bed to move downwardly through the sample vessel 12. A scraper 24 is used to separate a predetermined height of sample away from the bed. As samples are collected, they are separated into drying trays 23. This step is repeated until a number of samples are collected. Normally at least 8 samples will be required to generate coherent data for assessment.

The operation of the apparatus maybe described as follows: The test sample is placed into the sample vessel that is subsequently placed into the water reservoir. The test sample tube is suspended from the agitation arm of the agitation means. The water level is adjusted to be approximately 20 mm below the top of the sample tube at the bottom of its stroke. The sample is then "jigged" at a frequency of 1 cycle/second and an amplitude of approximately 60 mm.

The sample is sorted into a density continuum, from high density at the bottom to the lowest density at the top after approximately 40 minutes of operation. Tracers such as a glass sphere or marble (SG 2.5g/cc) are used to determine whether sorting is complete. Prior to the pulsing cycle, the glass sphere is placed on top of the sample bed in the sample tube. The sphere should have migrated to the bottom of the tube at the completion of the test. If the sphere is not at the bottom of the tube (in the first sample collected) the sample has not been fully sorted. At the end of the jigging period, the sample vessel is removed from the water, allowed to drain and then loaded into the sample fraction retrieval stand illustrated in Figure 4. The sample vessel is suspended in the sample fraction retrieval stand, which includes a clamp to hold the sample vessel a predetermined distance (normally approximately 25 mm) above a rubber mat. The rubber mat is mounted above a tray or similar to allow the removal of the particulate fractions according to their (generally visible) sorted sample horizons.

The screen is removed from the base of the sample vessel allowing the sample bed to move downwardly through the sample vessel. A scraper is used to separate a predetermined height of sample away from the bed. As samples are collected, they are separated into drying trays. This step is repeated until a number of samples are collected. Normally at least 8 samples are required to generate coherent data for assessment.

The collected and separated fractions are then typically dried and the dry mass of the fractions is recorded. The dried fractions are then milled for analysis and the ash% of each fraction calculated as outlined in Table 1 below. Table 1 - Trial Run of the preferred embodiment on coal particulate.

These results are used to generate a washability curve as illustrated in Figure 6.

The operational parameters of the apparatus are further illustrated through an explanation of a more comprehensive trial as follows: Trial 1 - Comprehensive Trial

This trial utilised a broad particle size range of -50 + 0.25 mm particles but the smaller -16 + 0.25 mm fraction was studied separately to the coarser -50 + 16 mm size range. The sample chamber used to hold the -16 mm sample of coal had a diameter of 150 mm. The base of the chamber was covered by a wire-mesh distributor screen with apertures of 250 μm. The chamber was located within a larger vessel, 280 mm in diameter. The analysis of the -50 +16 mm size fraction used two different inner/outer jigging chamber dimensions of 180/280 mm and 265/315 mm. The oscillation of the inner chamber was driven by a motor controlled rotating cam and shaft arrangement. The cam size regulates the height from which the vessel drops for each cycle, and consequently controls the water velocity through the inner vessel. The cam sizes examined in this study were 100, 150 and 180 mm in diameter, illustrated by the reference letter "D" in Figure 3.

For each experiment, nominally 4kg of a -16 +0.25 mm sample was added to the inner chamber vessel. This mass corresponded to a fixed bed height of 250mm. Nominally a 10- 15kg sample was tested for the -50 +16 mm fraction, which corresponded to a fixed bed height of approximately 500 mm. The chamber was then placed in the outer vessel and attached to the motor via a shaft. Water was added to the vessel until the level of water reached 25 mm below the top of the inner chamber. The motor was then switched on and the cycle commenced, m general, the cycle frequency was 1 cycle/s. At the end of the total jig time, the final packed bed was divided into segments. Again, the mass, apparent relative density (ARD), and ash % were determined for each layer. Analysis of -16 +0.25 mm size fraction To evaluate the performance of the jig over the size range -16 + 0.25 mm, a series of experiments were conducted to study the effect of varying two operational parameters. Firstly, the cam size was varied from 100 to 150, to 180 mm diameter, resulting in different water velocities through the inner vessel during the downward jig stroke by regulating the height from which the vessel drops for each cycle. Secondly, the jig cycle rate was adjusted between 0.5, 1 and 1.5 cycle/s. These conditions resulted in a test matrix of nine experiments which were analysed collectively to determine the optimal process conditions for generating washability data using the jig. Figures 7a, 7b and 7c show the effect of the cycle rate for the 100, 150 and 180 mm rotating cam experiments, respectively. Figure 7a shows data for the smallest rotating cam and shows the most significant deviation of the jig data from the float-sink yield ash curve. This is particularly evident at the knee of the curve, that is, the region where the curve gradient changes significantly. The effect of the cycle rate is less obvious, with the 0.5 cycle/s indicating a poor result compared to the 1 and 1.5 cycle/s experiments. Figure 7b shows the results for the medium sized rotating cam and indicates an improved comparison with the float-sink data. There appears to be a gradual improvement as the cycle rate is increased from 0.5 to 1.0 cycle/s, and is further

,5 enhanced for the 1.5 cycle/s experiment. The increase in cycle rate promotes fines drainage which provides a mechanism for fine mineral matter to return to the base of the vessel. Figure 7c show the comparison between the float-sink data and the largest rotating cam and indicates similar agreement as achieved by the medium sized cam. There is a notable improvement as the jig cycle rate is increased from 0.5 cycle/s to0 1.0 cycle/s, but deterioration when the rate was increased to 1.5 cycle/s. Although the high cycle rate promotes the fines return mechanism, the rapid jig cycle rate combined with the high velocity are counter productive in the sense that incomplete fluidisation occurs and consequently mixing rather than segregation dominates. This mixing results in a greater deviation of the jig data from the float-sink yield-ash curve, which5 is particularly noticeable in the low ash region.

From this study the optimal experimental conditions were determined as 1.0 jig cycle/s using the 180 mm rotating cam. The next services of experiments examined the effect of the number of cycles on the quality of the fractionation. The number of cycles from varied from 1800, 3600, 7200 to 14400 cycles, which0 corresponded to a 0.5, 1.0, 2.0 and 4.0 hour experimental time. Figure 7d shows the results for the optimal experimental conditions as a function of the experimental time. The results indicate that as the number of cycles increase there is an improvement in performance, with a diminishing benefit beyond 7200 cycles.

In the present specification and claims (if any), the word "comprising"5 and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present0 invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more combinations. In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

Claims:

1. A classification apparatus including i. a fluid container holding an amount of fluid, ii. a sample vessel for holding a sample amount of material to be classified, with a lower portion of the sample vessel in fluid communication with the fluid in the fluid container; and iii. an agitating mechanism to move the sample material relative to the fluid in the fluid container to agitate the sample material.

2. A classification apparatus according to claim 1 wherein the agitation mechanism moves the sample material in a vertical direction to take advantage of the effects of gravity on the sedimentation of the sample.

3. A classification apparatus according to claim 1 or claim 2 including a mechanical agitation or jigging apparatus.

4. A classification apparatus according to any one of the preceding claims wherein the fluid used is water.

5. A classification apparatus according to any one of the preceding claims wherein the fluid is provided as a static body in a closed fluid container.

6. A classification apparatus according to any one of the preceding claims wherein the fluid container is an elongate hollow vessel with an open top to contain the body of water into which the sample vessel least partially extends.

7. A classification apparatus according to any one of the preceding claims wherein the sample vessel is an elongate, hollow vessel with an open top.

8. A classification apparatus according to any one of the preceding claims wherein the sample vessel is provided a lower portion through which fluid can move but prevents egress or loss of particulate from the sample through the lower portion.

9. A classification apparatus according to claim 8 wherein the lower portion is provided with a base wall with at least a portion of screen material or sieve-like material.

10. A classification apparatus according to any one of the preceding claims wherein at least a portion of a lower end of the sample vessel is removable in order to harvest fractions of the sample following classification of the sample.

11. A classification apparatus according to any one of the preceding claims wherein the sample vessel is suspended from the agitation mechanism into the fluid container and the fluid therein.

12. A classification apparatus according to any one of the preceding claims wherein the sample vessel is removably mounted to the agitation means in order that it can be removed and attached to a sample fraction retrieval apparatus.

13. A classification apparatus according to any one of the preceding claims wherein the sample vessel is substantially taller than the height of the sample which it contains in order to have excess height to allow for expansion of the sample bed during the fluidisation stage of the operation.

14. A classification apparatus according to any one of the preceding claims wherein the agitation mechanism agitates/fluidises the sample periodically as opposed to constantly to give the fluidised sample time to settle.

15. A classification apparatus according to any one of the preceding claims wherein the agitation mechanism agitates the sample in a reciprocating motion.

16. A classification apparatus according to any one of the preceding claims wherein the sample vessel is lifted by the agitation mechanism and then allowed to fall under the force of gravity.

17. A classification apparatus according to claim 16 wherein the height to which the sample vessel is raised is alterable.

18. A classification apparatus according to any one of the preceding claims wherein the agitation mechanism is associated with at least one attachment arm to attach the sample vessel to the agitation mechanism, an upper end of at least one attachment arm is associated with a cam means which through its association with the at least one arm, is adapted to lift and drop the sample vessel in a cyclical manner.

19. A classification apparatus according to any one of the preceding claims wherein the agitation mechanism includes a substantially semi-circular cam plate mounted and powered for rotation about a horizontally oriented pivot towards one of the corners of the cam.

20. A classification apparatus according to any one of claims 1 to 3 wherein air is used as the fluid, the air injected or blown upwardly into the sample bed in intermittent bursts or pulses to allow for sedimentation time and effect.

21. A method for classifying particulate material according to specific gravity, the method including the steps of: iii. providing a jigging apparatus including a fluid container holding an amount of fluid, a sample vessel for holding a sample amount of material to be classified, with a lower portion of the sample vessel in fluid communication with the fluid in the fluid container; and an agitating mechanism to move the sample material relative to the fluid in the fluid container; iv. agitating the sample vessel for an optimum time period, t, and at an optimum fluid velocity of the fluid into the sample vessel.

22. The method according to claim 21 wherein the agitation is a cyclical process involving bed expansion and segregation through the pulsation of the particle bed by a current of water.

23. The method according to claim 21 or claim 22 wherein the agitation is a vertical agitation including two basic operational strokes, an upstroke which effects fluidisation of the sample bed and a downstroke which has a sedimentation effect on the fluidised sample bed.

24. The method according to claim 23 wherein the difference in height between the top of the upstroke and bottom of the downstroke is adjusted to give a optimal fluid velocity.

25. The method according to any one of claims 21 to 24 wherein the agitation speed is adjustable to an optimum cycle rate in cycles per second.

26. The method according to any one of claims 21 to 25 wherein agitation occurs for at least 3600 cycles or at least 1 hour.

27. The method according to any one of claims 21 to 25 wherein a tracer means is used to establish whether the sorting is complete.