This invention will particularly advantageously be applicable to drying and cooling of particulate materials, such as diamondiferous ore, after washing thereof and prior to screening thereof in mine workings, and such application should particularly be borne in mind when considering this specification.

In accordance with one aspect of the invention there is provided a method of drying a moist or wet particulate material, which method includes moving the material in a stream downwardly at least partially under gravity while causing the stream, as the material is moved downwardly, to follow a path which undergoes a plurality of changes in direction, and heating the material as it is moved, so that at least some moisture in the material evaporates, thereby at least partially drying the material.

The method may include assisting the moving of the material and regulating the rate at which it is moved, by inducing vibrations in the material.

The heating of the material may include heating a heating atmosphere to a temperature above that of the material, the downward moving of the material being through said heated heating atmosphere, so that heat is transferred from the heating

atmosphere to the material. The method may include passing the heating atmosphere along the path. The passing of the heating atmosphere along the path may be in a direction countercurrent to the direction of movement of the material.

The method may further include, after the heating, cooling the at least partially dried material. The heating and the cooling of the material may be carried out in-line and continuously, the cooling taking place as the material, in the stream, follows the path. The cooling of the material may be by having the downward moving of the material take place through a cooling atmosphere having a temperature below that of the material, so that heat is transferred from the material to the cooling atmosphere.

Naturally, the temperature to which the material is heated and the time which it is kept at this temperature will depend on various variables such as, for example, the nature of the material and the degree to which the material is to be dried.

Likewise, the temperature to which the at least partially dried material is cooled will depend on various variables such as, for example, the nature of the material and the required reduced temperature of the material to permit further treatment thereof.

Routine experimentation should be employed to yield acceptable values for a particular treatment scenario.

The method may also include extracting fines from the material. Extracting the fines may by extracting the atmosphere surrounding the material from the path, the fines being entrained in the extracted atmosphere.

In accordance with another aspect of the invention there is provided an assembly for drying a moist or wet particulate material, which assembly includes: a hollow housing defining an elongated treatment zone, the housing being provided with a material inlet leading into the treatment zone and a material outlet leading out of the treatment zone, the inlet and the outlet being spaced from each other along the length of the treatment zone, with the part of the treatment zone between the inlet and the outlet providing a flow path, the housing having an upright operative orientation or condition wherein the outlet is located lower than the inlet, to permit material introduced into the treatment zone via the inlet to move in a stream downwardly at least partially under gravity towards the outlet along the flow path; a plurality of guides arranged in the treatment zone for guiding movement of the material along the flow path, the guides being arranged for deflecting said stream of material to ensure that free or unobstructed fall of material under gravity from the material inlet to the material outlet is prevented; a vibration mechanism operatively connected to the housing for inducing vibrations in the housing, in the guides and in material in the treatment zone, for assisting movement of material along the flow path; and a heating arrangement for heating a heating part of the treatment zone and for heating material moving along said part of the treatment zone and causing at least some moisture in the material to evaporate, thereby at least partially drying the material.

The guides may be arranged such that material moving along the flow path cascades from one guide to another in series, the flow path changing direction at each guide.

The upright operative orientation or condition of the housing may be such that the treatment zone extends substantially vertically, with the guides comprising planar deflectors and in said operative upright orientation or condition being aligned at downwardly sloping angles, relative to the horizontal, with alternate deflectors projecting in opposing directions to define a said flow path which is tortuous and zigzags along its length.

The housing may be provided with a removable and replaceable liner constructed of a material having wear-resistant properties, the deflectors being secured to the liner. The liner may be constituted by a plurality of independently replaceable segments, which segments are arranged in series along the treatment zone, each segment having at least one deflector secured thereto.

Each guide may be at least partially protected by a replaceable layer of a material having wear-resistant properties.

The assembly may include a cooling device for cooling the treatment zone along a cooling part thereof spaced from the inlet by the heating part of the treatment zone, thereby to cool the at least partially dried material moving along the cooling part of the treatment zone. Thus, when the housing is in its upright operative orientation or condition, the heating part of the treatment zone will be located above the cooling part of the treatment zone. The housing may be provided with a cooling atmosphere inlet leading into the cooling part of the treatment zone for receiving a cooling atmosphere

from the cooling device, the cooling device being located outside the treatment zone and being in communication with the cooling part of treatment zone via the cooling atmosphere inlet. The assembly may further include an extraction vent leading out of the treatment zone, spaced between the material inlet and the material outlet, for venting the cooling atmosphere and fines entrained therein from the treatment zone.

The assembly may also include an extraction mechanism located outside the treatment zone and in communication with the treatment zone via the extraction vent, for extracting said cooling atmosphere and the fines entrained therein from the treatment zone.

The housing may be provided with a heating atmosphere inlet leading into the heating part of the treatment zone, for receiving a heating atmosphere introduced into the heating part of the treatment zone. The assembly may yet further include a heating atmosphere circulation device in communication with the treatment zone via the heating atmosphere inlet, for introducing a heating atmosphere into the heating part of the treatment zone.

The heating arrangement may include at least one heating element located in the heating part of the treatment zone. The heating arrangement may include a heating element for each guide in the heating part of the treatment zone, with each heating element being located downstream of an associated one of the guides in the direction from the material inlet to the material outlet. Thus, when the housing is in its upright operative orientation or condition, each heating element will be located below its associated guide, advantageously being secured thereto.

The housing may be provided with a vapour vent located at or adjacent the material inlet and leading out of the treatment zone, for venting evaporated moisture and fines from the treatment zone. The assembly may also include a vapour extraction 125 mechanism located outside the treatment zone and in communication with the treatment zone via the vapour vent, for extracting vapour and fines from the treatment zone.

The assembly may still further include a base for supporting the housing in its upright operative orientation or condition, the housing being movably connected to 130 the base, to accommodate lateral movement of the housing arising from operation of the vibration mechanism.

The base may include a vibration-absorbing arrangement for absorbing vibrations induced in the housing by the vibration mechanism.

135 The assembly may yet further include a securing formation connected to the housing adjacent the upstream end of the treatment zone in the direction from the material inlet to the material outlet, for securing the housing to an anchoring structure, the securing formation being connected to the housing via a vibration-absorbing 140 arrangement for absorbing vibrations induced in the housing by the vibration mechanism. Thus, upon operation of the vibration mechanism, little or no vibration will be transferred from the housing to the anchoring structure.

The invention is now described, by way of example, with reference to the 145 accompanying diagrammatic drawings.

In the drawings: Figure 1 shows, fragmentary, a schematic three-dimensional view of an assembly for drying a moist or wet particulate material in accordance with the invention; 150 and Figure 2 shows, schematically in part, a longitudinal sectional elevation of the assembly in accordance with the invention.

With reference to the drawings, an assembly for drying a particulate 155 material in accordance with the invention is generally indicated by reference numeral 10.

The assembly 10, as will become more apparent hereinafter, is also intended to cool the particulate material which it dries. The assembly 10 includes an elongated, rectangular vertically oriented hollow housing 12 of sheet metal construction defining an elongated treatment zone 14 of rectangular cross-section.

160 The housing 12 has a material inlet 16 provided adjacent the upper end thereof leading into the treatment zone 14 for introduction of a particulate material (not shown) into the treatment zone 14. At the lower end thereof, the housing 12 is provided with a material or product outlet 18 leading out of the treatment zone 14 and via which 165 particulate material which has been dried, leaves the treatment zone 14. The material inlet 16 and the material outlet 18 are thus longitudinally and vertically spaced from each other along the treatment zone 14, such that that part of the treatment zone 14 between the material inlet 16 and the material outlet 18 defines a flow path generally indicated by reference numeral 20. In use, as described hereinafter, particulate material which 170 enters the treatment zone 14 thus cascades or flows at least partially under gravity towards the product outlet 18 along the flow path 20.

A plurality of guides in the form of flat planar deflector plates 22 are located in the treatment zone 14. The deflector plates 22 are downwardly sloping and 175 alternate plates 22 project in opposing directions from opposing sides of the housing 12, such that the flow path 20 is a tortuous or labyrinthine path which zigzags along its length, as can be seen in Figure 2.

The housing is lined with a removable and replaceable liner constructed of 180 a material having wear-resistant properties. In particular, the liner is constituted by a plurality of independently removable and replaceable segments or cartridges 23, the segments 23 being rectangular in cross-section and arranged in series along the length of the treatment zone. Each segment 23 is slotted into a slot (not visible) provided by the housing 12, and, when located in its slot, is secured to the housing 12 by bolts (not 185 shown). Each of the segments has two deflector plates 22 secured thereto, the two reflector plates 22 secured to each segment 23 respectively projecting in opposing directions from opposing walls of the segment 23. The deflector plates 22, in turn, are also manufactured from a material having wear-resistant properties, such as mild steel or stainless steel, and are fixedly secured to the segments 23. Each segment 23 and it 190 associated deflector plates 22 thus form a unit which can independently be removed and replaced if the deflector plates 22 or walls of the segment 23 are worn. To this end, each segment 23 is provided with a pair of laterally outwardly protruding flanges 25, by means of which the segment 23, when the bolts which secure it to the housing 12 are released, can be removed from the housing 12.

195 The arrangement of the deflector plates 22 along the treatment zone 14 thus cause particulate material, which moves or flows in a stream along the flow path 20 in use, to cascade from one plate 22 to another in series while changing direction at each plate 22.

200 The assembly 10 further includes a vibration mechanism 24 (shown in concept only) connected to an upper part of the housing 12 for inducing vibrations in the housing 12 and, accordingly, in the deflector plates 22 and in particulate material in the treatment zone 14, for assisting the flow under gravity of the particulate material 205 downwardly along the flow path 20. The vibration mechanism 22 is of the kind which permits adjustment of the-intensity of vibrations generated. The vibration mechanism 22 is thus, in use, employed also to regulate the rate at which material move or flow through the treatment zone 14. The rate at which material is dried and cooled and, accordingly, the output rate of the assembly 10, can thus be regulated.

210 The assembly 10 yet further includes a heating arrangement or device which, in the embodiment shown, is in the form of an arrangement of a plurality of heating elements 26 respectively located below the deflector plates 22 in a heating-or upper part of the treatment zone 14, one heating element 26 for each plate 22, for 215 heating the treatment zone 14 along its heating-or upper part.

The assembly 10 also includes at least one temperature regulator or thermostat (not shown) for regulating and adjusting the temperature of the heating elements 26. Each temperature regulator or thermostat is operatively connected to an 220 adjustable control device for controlling operation thereof so that the temperature in the heating-or upper part of the treatment zone 14 is continuously controlled. Thus, the temperature in the heating-or upper part of the treatment zone 14 can be adjusted to a desired value and maintained at said desired value. When the assembly 10 is employed for drying and cooling of diamondiferous ore, as in the present embodiment, the 225 temperature in the heating-or upper part of the treatment zone is controlled between 90° -120°C. Naturally, the temperature can, depending on the operating conditions, be higher, or even lower, than the aforementioned temperature range.

A cooling device in the form of a blower 28 is in communication with the 230 treatment zone 14 via a cooling atmosphere inlet 30 provided in a cooling-or lower part of the housing 12. A flow pipe 34 connects the outlet of the blower 28 with the cooling atmosphere inlet 30. A cooling atmosphere comprising air can thus be introduced into the cooling-or lower part of the treatment zone 14 for cooling dried particulate material, which cascades or flows downwardly, along the flow path 20, through the cooling-or 235 lower part of the treatment zone 14. In the present embodiment, the particulate material is cooled to a temperature below 40°C, to permit further processing or treatment thereof.

A valve 38 (shown in concept only in Figure 2) is provided in the pipe 34 for regulating flow of the cooling air from the blower 28 into the treatment zone 14.

240 The blower 28 is also in communication with the heating-or upper part of the treatment zone 14 by means of a pipe 36 which leads from the outlet of the blower 28 to a heating atmosphere inlet 32 provided in the heating-or upper part of the housing 12. A heating atmosphere in the form of air can thus be introduced by means of the blower 28 into the upper part of the treatment zone 14 to assist with heat transfer from 245 the heating elements 26, and accordingly from the plates 22 which are heated by the heating elements 26, to particulate material in the heating-or upper part of the treatment zone 14, as described hereunder. A valve 40 (also only shown in concept in Figure 2) is provided in the pipe 36 for regulating flow of air from the blower 28 to the heating-or upper part of the treatment zone 14. The blower 28 thus acts as a heating atmosphere 250 circulation device.

In another embodiment (not shown), the assembly 10 includes a heating device which supplies heated-air or gas to the heating-or upper part of the treatment zone 14, the heating device being in communication with the upper part of the treatment 255 zone 14 via the heating inlet 32.

The assembly 10 also includes an extraction vent 42 leading out of the treatment zone 14 for venting, from the treatment zone 14, a cooling atmosphere, which cooling atmosphere is in the form of air from the pipe 34, and unwanted fines entrained 260 in said cooling atmosphere after the air has cooled the particulate material. The extraction vent is located more or less between the heating part and the cooling part of the treatment zone 14. Although not shown, the assembly 10 can thus also include an extraction mechanism such as a fan or blower, which mechanism is in communication with the treatment zone 14 via the extraction vent 42 for extracting said cooling 265 atmosphere and said unwanted fines entrained therein from the treatment zone 14, and for feeding it to a dust extraction plant (not shown).

The rectangular cross-section of the housing 12 is, at a top thereof, somewhat constricted to provide a vapour vent 44 leading out of the treatment zone 14 270 for venting the heating atmosphere/air and the evaporated moisture from the treatment zone 14. The vapour vent 44, in Figure 2, is shown open to the atmosphere but, instead, may be in communication, via an extraction mechanism (not shown), with said dust extraction plant, for extracting fines entrained therein. A pipe 43 shown in Figure 1 provides communication between the extraction vent 44 and said extraction mechanism.

275 The upper part of the housing 12 is clad with an insulating cladding 56 which insulates the heating-or upper part of the treatment zone 14 against heat loss.

The housing 12 is mounted on a base or plinth 46. The base or plinth 46, 280 in turn, is fixedly mounted on a substrate (not shown) on which the assembly 10 is supported. The housing 12 is pivotally mounted via rubber mounting pads 45 on the base or plinth 46 to accommodate lateral movement of the upper part of the housing 12 during operation of the vibration mechanism 24. The rubber mounting pads 45 also serve as vibration-absorbers, so that, during operation of the vibration mechanism 24, 285 little or no vibration is transferred to said substrate on which the assembly 10 is supported.

The upper end of the housing 12 is secured to an anchoring structure 47 which does not form part of the assembly 10 and, accordingly, is indicated in broken 290 lines. The upper end of the housing 12 is secured to the anchoring structure 47 by means of a securing formation comprising a pair of elongated beams 48,50 straddling the housing 12. The beams 48,50, in turn, are respectively secured to the upper end of the housing 12 by means of two sets of coil springs 52,54, each set 52,54 including four springs. The beams 48,50 and their springs 52,54 thus form a vibration-absorbing 295 arrangement, such that, upon operation of the vibration mechanism 24, little or no vibration is transferred from the, housing 12 to the anchoring structure 47.

In the embodiment shown, the assembly 10 is a permanent installation. In other embodiments which are not shown, the assembly 10 can be constructed such that 300 it is a mobile unit.

In use, a particulate material, such as diamondiferous ore, which has been washed, is introduced into the treatment zone 14 via the material inlet 16. The particulate wet or moist material then moves, in a stream, at least partially under gravity 305 downwardly along the flow path 20 towards the material or product outlet 18. For illustration purposes, flow of particulate material along the flow path 20 is indicated by arrows 58 in Figure 2. Vibrations are induced by the vibration mechanism 24 via the housing 12 and the plates 22 in the particulate material as it flows along the flow path 20 to assist the flow thereof, and to regulate the flow of the material.

310 The upper part of the housing 12 is heated by means of the heating elements 26 and, accordingly, the particulate material in the heating-or upper part of the treatment zone 14 is heated as it cascades downwardly along the heating-or upper part of the treatment zone 14, such that at least some of the moisture in the particulate 315 material evaporates. The particulate material is thus at least partially dried in the heating-or upper part of the treatment zone 14. As the particulate material moves or flows downwardly through the upper part of the treatment zone 14, it is successively deflected by means of the deflector plates 22 such that it undergoes a plurality of changes in direction, one at each plate 22. The flow path 20 along which the particulate 320 material moves thus, as mentioned, zigzags along its length.

Air is introduced into the upper part of the housing 12 via the heating atmosphere inlet 32 by means of the blower 28. The air so introduced moves upwardly along the flow path 20, i. e. in a direction countercurrent to that of the movement of the 325 particulate material, and exits the treatment zone 14 via the evaporation vent 44.

Evaporated moisture is thus entrained in the air introduced via the heating inlet 32. As the air moves upwardly towards the vent 44 the air is heated by the heating elements 26 and the plates 22 and in turn heats the particulate material, thus assisting in transfer of heat from the heating elements 26 and the plates 22 to the particulate material.

330 The cooling-or lower part of the housing 12 is kept at a temperature more or less equal to ambient temperature by means of introducing cooling air thereinto via the cooling atmosphere inlet 30 by means of the blower 28. As the particulate material cascades through the cooling-or lower part of the treatment zone 14, it is cooled by 335 means of the cooling air flowing upwardly, countercurrent thereto. The cooling air so introduced thus forms a cooling atmosphere. After the cooling atmosphere has cooled the particulate material, it exits the treatment zone 14, mainly via the extraction vent 42.

Unwanted fines are entrained in the cooling atmosphere, and are thus also extracted via the extraction vent 42.

340 The particulate material which is at least partially dried in the heating-or upper part of the treatment zone 14, is thus cooled, in the cooling-or lower part of the treatment zone 14, to a temperature sufficiently low to permit or facilitate immediate further treatment thereof. As earlier mentioned, the particulate material is typically 345 cooled to a temperature below 40°C. The dried and cooled particulate material exits the treatment zone 14 via the product outlet 18 from where it is conveyed away from the assembly 10 by means of a conveyor system 60 (only shown in concept and in broken lines, and not forming part of the assembly 10) for further treatment. As can be seen in the drawings, a chute assembly 62 is provided at the material or product outlet 18 for 350 guiding the material flowing from the outlet onto a belt of the conveyor system 60.

The invention as described and illustrated thus provides an in-line and continuous process and assembly for drying and cooling particulate material, which is particularly suitable for drying diamondiferous ore, which requires to be relatively cool 355 after drying thereof, for example to permit and/or facilitate further treatment by means of an X-ray sorter.