BACKGROUND OF THE INVENTION

This invention relates to washers used in metal refining processes, and more particularly, washers for de-scaling activated carbon, for example, carbon loaded with a precious metal.

To this end, there are generally two main processes available for gold concentration and recovery: zinc precipitation, and electrowinning. Zinc precipitation involves crushing and grinding ore containing gold, and then combining the ground ore with a water and caustic cyanide solution. The resulting mud-like pulp is moved to a settling tank where the coarser gold- laden solids move to the bottom via gravity, and a lighter first pregnant solution of water, gold, and cyanide moves to the top and is removed for further processing. The gold-laden solids are agitated and aerated in a separate agitated leach process where oxygen reacts to leach the gold into the water, caustic, and cyanide solution forming a second pregnant solution. The second pregnant solution passes through a drum filter which further separates remaining solids. The first and second pregnant solutions are combined with zinc to precipitate out the dissolved gold. The resulting precipitated gold concentrate may then be smelted to produce refined gold bar.

Electrowinning typically involves extracting gold from an electrolyte produced by combining activated carbon with a pregnant gold solution in a batch process step. The activated carbon absorbs gold contained within the pregnant solution, and becomes loaded with gold removed from the pregnant gold solution. The loaded carbon is then "de-scaled" by sequentially washing it in three batch process steps to remove ore residue. First, the loaded carbon is moved to a washing tank and then the tank is filled with a dilute acid solution. The washing tank is then drained and the used dilute acid solution is pumped away and disposed. The same washing tank is then filled with water to rinse remaining acid from the loaded carbon. The water becomes slightly acidic during this process. In a similar fashion to the dilute acid, the used (slightly acidic) rinse water is also drained from the washing tank, pumped away, and disposed. Lastly, the tank is filled with a caustic solution, and the loaded carbon is washed in the caustic. The used caustic is then drained from the tank, pumped away, and disposed. An optional final water rinse step may be performed by again, filling the washing tank with water, rinsing caustic residue from the loaded carbon, and then draining the tank of the caustic water. The used rinse water is then typically pumped away and disposed. The loaded carbon is then added to a water, caustic, and cyanide strip solution. The strip solution/loaded carbon slurry then undergoes an elution process where high temperatures and pressures are used to "re-leach" gold from the loaded carbon into the strip solution of water, caustic, and cyanide to form an electrolyte. The electrolyte is then moved to an electrowinning cell where wire cathodes collect deposited gold concentrate. The cathodes are then removed for cleaning in a batch process step, wherein the gold concentrate is removed from the cathodes for smelting.

Problems associated with the abovementioned processes are numerous. For instance, conventional de-scaling processes use "batch" process steps. This requires constant manpower, time, and energy to continually fill and drain the washing tank with different solutions.

Moreover, such batch processes typically discard expensive acid, caustic, and/or other reagents after each use. This leads to high overhead costs (e.g., purchasing cost, disposal cost) and potentially creates environmental hazards. Furthermore, each time a conventional washing tank is drained and re-filled with a different washing agent, carbon (and precious gold attached thereto) may be lost due to system inefficiencies (e.g., heat, friction, pump design, piping elbows, and discarded fluid). In some instances, as many as four tanks and ten pumps may be required with batch de-scaling processes, for example, when using different washing tanks for each rinse step. This increases both initial overhead costs and overall plant footprint. The process of using zinc to precipitate precious metals out of pregnant solutions is also costly, may be less efficient for large-scale operations, works for only certain metals, and may result in less precious metal recovery.

OBJECTS OF THE INVENTION

It is, therefore, an object of the invention to provide an improved washer configured for continuous washing of particulate, thereby avoiding the aforementioned problems associated with sequential batch washing processes.

It is also an object of the invention to provide an improved washer wherein washing medium is continuously recycled and reused, thereby avoiding particulate loss and overhead costs.

Moreover, an object of the invention is to provide an improved method for de-scaling activated carbon loaded with a precious metal.

Another object of the invention is to improve theefficiency of a precious metal recovery process.

Yet another object of the invention is to prevent carbon loss and maximize total precious metal recovery.

These and other objects of the invention will be apparent from the drawings and description herein. Although every object of the invention is believed to be attained by at least one embodiment of the invention, there is not necessarily any one embodiment of the invention that achieves all of the objects of the invention.

SUMMARY OF THE INVENTION A washer for particulate material comprises, in accordance with some embodiments of the invention, a chamber adapted for retaining a fluidization medium; an inlet adapted for receiving a feed containing particulate; a fluidized bed distribution panel adapted for fluidizing the particulate in the presence of said fluidization medium; an opening adapted to pass particulate and fluidization medium from the chamber; and a screen adapted to filter the particulate..

According to some embodiments, the washer may comprise multiple chambers, inlets, fluidized bed distribution panels, openings, and screens. . According to some embodiments, a fluidization medium such as an acid, caustic, or water may be provided to a chamber. According to some embodiments, one or more recirculation tanks may be provided for collecting spent fluidization medium. According to some embodiments, one or more weirs, channels, or drains for capturing spent fluidization medium may be provided. According to some embodiments, spent fluidization medium may be recycled by transporting it from a recirculation tank to a respective chamber.

A washing tank for a modular washer is also disclosed. According to some

embodiments, the washing tank generally comprises a tubular sidewall, a bottom wall provided at a lower end of said sidewall, at least one chamber defined between the sidewall and bottom wall and adapted for retaining a fluidization medium, an inlet for receiving particulate, an opening adapted to pass particulate and a fluidization medium from the chamber, a screen, and a fluidized bed distribution panel adapted for fluidizing particulate in the presence of said fluidization medium. The washing tank may comprises a recirculation tank, weir, and/or a channel.

A method of washing is also disclosed. The method comprises, in accordance with some embodiments of the invention, providing a washer having a chamber adapted for retaining a fluidization medium; an inlet; a fluidized bed distribution panel adapted for fluidizing particulate in the presence of said fluidization medium; an opening adapted to pass said particulate and fluidization medium from the chamber; and a screen adapted to filter said particulate; providing a fluidization medium to said chamber; feeding particulate into said chamber of the washer via said first inlet; filtering particulate with said screen; fluidizing particulate in said chamber with said fluidization medium; and, extracting particulate and fluidization medium from the chamber.

According to some embodiments, fluidization medium may be separated from the particulate and captured. According to some embodiments, the captured fluidization medium may be recycled by transporting the fluidization medium back to a respective chamber.

According to some embodiments, the fluidization medium may comprise acid, water, or caustic.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an isometric cutaway view of a washer according to some embodiments; FIG. 2 shows a top plan view of the washer of FIG. 1;

FIG. 3 shows a vertical sectional view of the washer of FIGS. 1 and 2, taken on line III- III in FIG. 2;

FIG. 4 is a right side view of the washer of FIGS. 1-3;

FIG. 5 is a left side view of the washer of FIGS. 1-4;

FIG. 6 is a front view of the washer of FIGS. 1-5;

FIGS. 7A and 7B are close-up views of the first opening shown in FIGS. 1 and 6, respectively;

FIG. 8 schematically illustrates a first sequence operation of the washer;

FIGS. 9 and 10 outline operational steps of a continuous washing process according to some embodiments; FIGS. 11 and 12 show a washing tank which may form a portion of a modular washer according to some embodiments; and

FIG. 13 shows a modular washer comprising a plurality of washing tanks as shown in FIGS. 11 and 12.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-8 show a washer 10 for cleaning a particulate material. The particulate material to be cleaned may be any material of size, shape, and density which can be fluidized by a fluidization medium. For example, in some non-limiting embodiments, washer 10 may advantageously be used to de-scale activated carbon particulate loaded with gold in preparation for creating a an electrolyte for electrowinning, wherein the fluidization medium may be selected from solutions containing water, acid, and/or caustic.

Washer 10 comprises a bottom surface 60, back surface 62, front surface 64, left side surface 66, and right side surface 68. While not shown, the washer 10 may optionally comprise a top surface or cover to contain fluids and particulate. The washer 10 comprises one or more chambers, for instance, a first chamber 20, a second chamber 30, and a third chamber 40. A first divider 92 separates the first chamber 20 from the second chamber 30, a second divider 94 separates the second chamber 30 from the third chamber 40, and a third divider 96 may separate the third chamber 40 from a third recirculation tank 49 as will be discussed hereinafter.

Particulate material 120 enters the washer 10 via a first inlet 22 associated with the first chamber 20. The first chamber 20 is filled with a first fluidization medium, for example, a strong or dilute acid. A first baffle 72 may be employed to separate the first inlet 22 from the first chamber 20 and increase the residence time of the particulate 120 within the first chamber

20. Guided by the first baffle 72, the incoming particulate material 120 may have a downward flow 100, falling towards the bottom of the first chamber 20 where it approaches a first fluidized bed distribution panel 21. The first fluidized bed distribution panel 21 may comprise a perforated panel with small openings. The openings in the perforated panel may be large enough to pass the first fluidizing medium from a first recirculation inlet 23 a through the first fluidized bed distribution panel 21 and into the first chamber 20, but small enough to prevent particulate material 120 from falling through the bed distribution panel 21 and into the first recirculation inlet 23 a. Particulate material 120 is fluidized and becomes suspended within the first chamber

20 as it flows 102 around the first chamber 20. As more clearly shown in FIG. 8, the particulate

120 is suspended to an extent 104 where it is no longer suspended in the first fluidization medium 130 due to gravitational forces. A first opening 28 is positioned proximate to the extent of fluidization 104 of particulate 120. The particulate 120, still wetted by the first fluidization medium, flows 110 through the first opening 28 and over a first screen 26, where the first fluidization medium drains 112 from the particulate 120 into a first recirculation tank 29.

Clarified first fluidization medium 130 which is free from particulate 120 rises above the extent of fluidization 104 to a top level 106, and flows 108 over a first weir 24 provided around top portions of the first chamber 20 and into a first channel 82. The first channel 82 and first weir 24 may be provided circumferentially around top portions of the first chamber 20 as shown, but may also be provided centrally without limitation. The first channel 82 may comprise one or more first channel drains 25 which move first fluidization medium 130 within the first channel 82 to the first recirculation tank 29.

Spent first fluidization medium 130 temporarily resides in the first recirculation tank 29.

A first overflow outlet 27 may be provided to purge the tank 29 when the first recirculation tank

29 becomes too full of spent first fluidization medium 130. Spent first fluidization medium 130 that exits the tank 29 through the first overflow outlet 27 may go to a holding tank (not shown) for holding, filtering, recycling, future use, or further processing. One or more first recirculation outlets 23b may also be provided to the first recirculation tank 29 to deliver spent first fluidizing medium 130 back to the first recirculation inlet 23a for continued use within the first chamber

20. The first fluidization medium 130 may undergo one or more processing steps during its journey between the first recirculation tank 29 and the first recirculation inlet 23a. For instance, one or more filtering steps may take place, or additional virgin first fluidization medium (e.g., acid) or a dilutant may be added to keep the chemistry of the first chamber 20 balanced. These intermediate processing steps may be computer controlled with a loop feedback control system, wherein sensors continuously monitor pH levels at various locations within the washer 10. One or more pumps (not shown) may help transport spent first fluidization medium 130 from the first recirculation tank 29 to the first recirculation inlet 23 a.

After the wetted particulate material 120 exits the first opening 28, it is strained as it passes over the first screen 26. It then enters the second chamber 30 via a second inlet 32. The second chamber 30 is filled with a second fluidization medium, which may or may not be the same as the first fluidization medium. For example, the second fluidization medium may comprise water or another substantially pH-neutral rinsing solution. A second baffle 74 may be employed to separate the second inlet 32 from the second chamber 30 and increase the residence time of the particulate 120. Guided by the second baffle 74, the particulate material flows downward and falls towards the bottom of the second chamber 30 where it approaches a second fiuidized bed distribution panel 31. The second fiuidized bed distribution panel 31 may comprise a perforated panel with small openings (e.g., a screen, or filter). The openings in the panel 31 may be large enough to pass the second fluidizing medium from a second recirculation inlet 33a through the second fiuidized bed distribution panel 31, and into the second chamber 30, but small enough to prevent particulate material 120 from falling through the bed distribution panel 31 and into the second recirculation inlet 33 a. Particulate material 120 is fiuidized and becomes suspended within the second chamber 30 as it flows around the second chamber 30. As described above for the first chamber 20, the particulate 120 is similarly suspended to an extent where it is no longer suspended in the second fluidization medium due to gravitational forces. A second opening 38 is positioned proximate to the extent of fluidization of particulate 120. The particulate 120, still wetted by the second fluidization medium, flows through the second opening 38 and over a second screen 36, where the second fluidization medium drains from the particulate 120 into a second recirculation tank 39. Clarified second fluidization medium (free from particulate 120) rises above the extent of fluidization to a top level, and flows over a second weir 34 provided around top portions of the second chamber 30 and into a second channel 84. The second channel 84 and second weir 34 may be provided circumferentially around top portions of the second chamber 30 as shown, but may also be provided centrally without limitation. The second channel 84 may comprise one or more second channel drains 35 which move the clarified second fluidization medium within the second channel 84 to the second recirculation tank 39.

Spent second fluidization medium temporarily resides in the second recirculation tank 39.

A second overflow outlet 37 may be provided to purge the tank 39 when the second recirculation tank 39 becomes too full of spent second fluidization medium. Spent second fluidization medium that exits the tank 39 through the second overflow outlet 37 may go to a holding tank

(not shown) for holding, filtering, recycling, future use, or further processing. One or more second recirculation outlets 33b may also be provided to the second recirculation tank 39 to deliver spent second fluidizing medium back to the second recirculation inlet 33a for continued use within the second chamber 30. The second fluidization medium may undergo one or more processing steps during its journey between the second recirculation tank 39 and the second recirculation inlet 33 a. For instance, one or more filtering steps may take place, or additional virgin second fluidization medium (e.g., water) or a dilutant may be added to keep the chemistry of the second chamber 30 balanced. These intermediate processing steps may be computer controlled using a plurality of sensors with a loop feedback control system as discussed above.

In some instances, (e.g., when the second fluidization medium is water), any one or more of the overflow outlet 37, second recirculation outlets 33b, or recirculation tank 39 may be tapped to or otherwise piped to a larger plant water system. One or more pumps (not shown) may help transport spent second fluidization medium from the second recirculation tank 39 to the second recirculation inlet 33 a.

After the wetted particulate material 120 exits the second opening 38, it is strained as it passes over the second screen 36. It then enters the third chamber 40 via a third inlet 42. The third chamber 40 is filled with a third fluidization medium, which may or may not be the same as the first or second fluidization mediums. For example, the third fluidization medium may comprise a solution of caustic and/or another rinsing agent. A third baffle 76 may be employed to separate the third inlet 42 from the third chamber 40 and increase the residence time of the particulate 120 within the third chamber 40. Guided by the third baffle 76, the particulate material flows downward and falls towards the bottom of the third chamber 40 where it approaches a third fluidized bed distribution panel 41. The third fluidized bed distribution panel

41 may comprise a perforated panel with small openings. The openings in the perforated panel may be large enough to pass the third fluidizing medium from a third recirculation inlet 43 a through the third fluidized bed distribution panel 41, and into the third chamber 40, but small enough to prevent particulate material 120 from falling through the bed distribution panel 41 and into the third recirculation inlet 43 a. Particulate material 120 is fluidized and becomes suspended within the third chamber 40 as it flows around the third chamber 40. As described above for the first chamber 20, the particulate 120 is suspended to an extent where it is no longer suspended in the third fluidization medium due to gravitational forces. A third opening 48 is positioned proximate to the extent of fluidization of particulate 120. The particulate 120, still wetted by the third fluidization medium, flows through the third opening 48 and over a third screen 46, where the third fluidization medium drains from the particulate 120 into a third recirculation tank 49. Clarified third fluidization medium rises above the extent of fluidization to a top level, and flows over a third weir 44 provided around top portions of the third chamber 40 and into a third channel 86. The third channel 86 and third weir 44 may be provided

circumferentially around top portions of the third chamber 40 as shown, but may also be provided centrally without limitation. The third channel 86 may comprise one or more third channel drains 45 which move the third fluidization medium within the third channel 86 to the third recirculation tank 49.

Spent third fluidization medium temporarily resides in the third recirculation tank 49. A third overflow outlet 47 may be provided to purge the tank 49 when the third recirculation tank

49 becomes too full of spent third fluidization medium. Spent third fluidization medium that exits the tank 49 through the third overflow outlet 47 may go to a holding tank (not shown) for holding, filtering, recycling, future use, or further processing. One or more third recirculation outlets 43b may also be provided to the third recirculation tank 49 to continuously deliver spent third fluidizing medium back to the third recirculation inlet 43 a for use within the third chamber

40. The third fluidization medium may undergo one or more processing steps on its journey between the third recirculation tank 49 and the third recirculation inlet 43 a. For instance, one or more filtering steps may take place, or additional virgin third fluidization medium (e.g., caustic) or a dilutant may be added to keep the chemistry of the third chamber 40 balanced. As previously mentioned, these intermediate processing steps may be controlled using sensors strategically placed within the washer 10 itself, or placed along conduits connected to the washer 10. One or more pumps (not shown) may help transport spent third fluidization medium from the third recirculation tank 49 to the third recirculation inlet 43 a.

As can be seen in the figures, one or more mounts 50 may be provided to the washer 10 for securement to a floor or surrounding foundation or structure. Moreover, as shown in FIGS. 7A and 7B, any of the first 28, second 38, or third 48 openings may be adjustable to

accommodate different process-specific flow rates. For instance, as shown, the first opening 28 may comprise an adjustable aperture 28a, a moveable gate 28c defining a portion of said adjustable aperture 28a and having a block 28f and a threaded hole 28g thereon, a track 28b on which the moveable gate 28c rides, a shaft 28j having a threads 28d thereon extending through the gate 28c and rotating freely within one or more bearings 28e, 28i, and a wheel or crank 28h attached to the shaft 28j.

FIGS. 9 and 10 schematically illustrate a method 1000 of sequentially and continuously washing a particulate according to one embodiment. For demonstrative purposes only, the particulate may be an activated carbon loaded with a precious metal (e.g., gold), the first fluidizing medium may comprise an acidic solution, the second fluidizing medium may comprise an aqueous solution, and the third fluidizing medium may comprise a caustic solution as shown. It should be understood, however, that other particulates, fluidizing mediums, and combinations thereof may be used for different washing processes without limitation.

The washing process 1000 begins with the step of providing 1002 a feed particulate. The feed particulate is transported to and fed 1004 into the washer where it enters a first stage wash basin. In the first stage wash basin, particulate is fluidized 1006 with a first stage fluidization medium such as a rinsing solution comprising one or more reagents. The particulate moves throughout the first stage wash basin until it eventually exits 1008 the first stage wash basin. The exiting particulate is screened 1010 to drain and capture 1012 residual first stage fluidization medium. The captured first stage fluidization medium may optionally undergo secondary processes 1014, after which it may be fed 1016 back into the first stage wash basin to complete the circuit.

The particulate exiting the first stage wash basin is then fed 1018 into a second portion of the washer where it enters a second stage wash basin. In the second stage wash basin, particulate is similarly fluidized 1020 with a second stage fluidization medium. The second stage fluidization medium may be any solution adapted to clean the particulate. The

fluidizing/cleaning medium in the second stage wash basin may be the same as the

fluidizing/cleaning medium used for the first stage wash basin, or it may be different.

The particulate moves throughout the second stage wash basin until it eventually exits 1022 the second stage wash basin. The exiting particulate may be screened 1024 again to drain and capture 1026 residual second stage fluidization medium. The captured second stage fluidization medium may optionally undergo secondary processes 1028, after which it may fed 1030 back into the second stage wash basin to complete the circuit.

The particulate exiting the second stage wash basin may be fed 1032 into a third portion of the washer where it enters a third stage wash basin. In the third stage wash basin, particulate is similarly fluidized 1034 with a third stage fluidization medium which may be configured to clean the particulate. The fluidizing/cleaning medium in the third stage wash basin may be the same as the fluidizing/cleaning mediums used for the first and second stage wash basins, or it may be different.

The particulate moves throughout the third stage wash basin until it eventually exits 1036 the third stage wash basin. The exiting particulate may be screened 1038 to drain and capture 1042 residual third stage fluidization medium. The captured third stage fluidization medium may optionally undergo secondary processes 1044, after which it may fed 1046 back into the third stage wash basin to complete the circuit.

The particulate exiting the third stage wash basin may be captured and moved to one or more downstream processes 1040 (for example, elution and electrowinning processes) and the washing process is finished 1048. In the particular embodiment shown, step 1040 may comprise making a strip solution from the particulate exiting the third stage wash basin by combining it with water, caustic, and cyanide.

As shown in FIG. 13, washers may be modular. For example, in some embodiments, a washer 210 may comprise one or more separate washing tanks 200, 200', 200" connected in series in order to provide flexibility in customizing plant layout and/or reduce overall footprint. In some instances, the washing tanks 200, 200', 200" may comprise similar or different fluidization mediums. For example, in some embodiments, a first washing tank 200 may comprise a strong or dilute acid solution, whereas second 200' and third 200" washing tanks comprise aqueous and caustic solutions, respectively. While not required, washing tanks 200, 200', 200" may be "universal" in nature and may be configured with a tubular (e.g., cylindrical or prismatic extrusion) shape as shown in order to reduce manufacturing costs.

FIGS. 1 1 and 12 illustrate a first washing tank 200 according to some embodiments.

First washing tank 200 generally comprises a first chamber 220, a first fluidized bed distribution panel 221, a first inlet 222, a first recirculation inlet 223a, a first recirculation outlet 223b, a first weir 224, a first screen 226, a first overflow outlet 227, a first discharge outlet 228, a first recirculation tank 229, a bottom wall 260, an inner tubular wall 266, an outer tubular wall 268, and a first channel 282 defined between the inner tubular wall 266 and outer tubular wall 268 adjacent the first weir 224. The first screen 226 serves to separate fluid from incoming particulate by straining/filtering. The fluid separated from the particulate is maintained in the first recirculation tank 229, and may be removed through first recirculation outlet 223b or by removing the first screen 226 and pumping said drained fluid out of the tank 229. The first recirculation outlet 223b may be sealed during operation, coupled to a holding tank, or otherwise configured to feed upstream process.

Turning again to FIG. 13, a first fluidization medium such as a strong or dilute acid solution may occupy a first washing tank 200. In use, incoming particulate 250 (e.g., activated carbon loaded with a precious metal such as gold) flows into the first chamber 220 of the first washing tank 200 through the first inlet 222 and moves over the first screen 226. Fluid which may be present with the incoming particulate 250 is drained and enters the first recirculation tank 229. The screened incoming particulate subsequently falls towards the first fluidized bed distribution panel 221 and is fluidized within the first chamber 220 by a flow of first fluidization medium entering the first recirculation inlet 223a and passing through distribution panel 221. Similarly to what is shown in FIG. 8, clarified first fluidization medium pours over the first weir 224 and into the first channel 282. Thereafter, the clarified first fluidization medium exits the first washing tank 200 via outlet 227 and optionally feeds the first recirculation inlet 223a and first fluidized bed distribution panel 221.

A slurry 252 of particulate and first fluidization medium exits the first washing tank 200 through first discharge opening 228 and enters a second washing tank 200' through second inlet

232. The slurry 252 may be conveyed to the second washing tank 200' using only gravitational forces, or the slurry 252 may be conveyed to the second washing tank 200' using one or more pumps (not shown). A second fluidization medium such as a substantially pH-neutral aqueous solution may occupy the second washing tank 200'. In use, the slurry 252 of particulate and first fluidization medium flows into the second chamber 230 and over a second screen 236 or equivalent filter. The second screen 236 serves to separate first fluidization medium from the particulate, wherein drained first fluidization medium is maintained in a second recirculation tank 239, but may be removed through second recirculation outlet 233b or by removing the second screen 236 and pumping said drained first fluidization medium out of the tank 239. The second recirculation outlet 233b may be coupled to a holding tank, filtering apparatus, secondary downstream process, or otherwise configured to feed one or more upstream processes. For instance, as schematically indicated by path 253, the second recirculation outlet 233b may be operatively connected to the first recirculation inlet 223a to fluidize particulate within the first washing tank 200. Though not shown, one or more pumps may be disposed between the outlet 233b and inlet 223a.

After passing over second screen 236, particulate subsequently falls towards a second fluidized bed distribution panel 231 and is fiuidized within the second chamber 230 by a flow of second fluidization medium entering the second recirculation inlet 233 a and passing through panel 231. Similarly to what is shown in FIG. 8, clarified second fluidization medium pours over a second weir 234 and into a second channel 284, where it exits the second washing tank 200' via outlet 237 and optionally feeds the second recirculation inlet 233 a and second fiuidized bed distribution panel 231 as schematically illustrated by path 254.

A slurry 255 of particulate and second fluidization medium exits the second washing tank

200' through second discharge opening 238 and enters a third washing tank 200" through a third inlet 242. The slurry 255 may be conveyed to the third washing tank 200" using only gravitational forces, or the slurry 255 may be conveyed to the third washing tank 200" using one or more pumps (not shown). A third fluidization medium such as a caustic solution may occupy the third washing tank 200". In use, the slurry 255 of particulate and second fluidization medium flows into the third chamber 240 and over a third screen 246 or equivalent filter. The third screen 246 serves to separate second fluidization medium from the incoming particulate, wherein the separated second fluidization medium is maintained in a third recirculation tank 249. The second fluidization medium may be removed from the tank 249 via a third recirculation outlet 243b or by removing the third screen 246 and pumping said drained second fluidization medium out of the tank 249. The third recirculation outlet 243b may be coupled to a holding tank, filtering apparatus, secondary process, or otherwise configured to feed one or more upstream processes. For instance, as schematically indicated by path 256, the third recirculation outlet 243b may be operatively connected to the second recirculation inlet 233 a to help fluidize particulate within the second washing tank 200'. Though not shown, one or more pumps may be disposed between the outlet 243b and inlet 233 a.

After passing over third screen 246, particulate subsequently falls towards a third fluidized bed distribution panel 241 and is fluidized within the third chamber 240 by a flow of third fluidization medium entering the third recirculation inlet 243a and passing through the panel 241. Similarly to what is shown in FIG. 8, clarified third fluidization medium pours over a third weir 244 and into a third channel 286, where it exits the third washing tank 200" via outlet 247 and optionally feeds third recirculation inlet 243a as indicated by path 257.

A slurry 258 of particulate and third fluidization medium exits the third washing tank 200" through third discharge opening 248 and may be subsequently screened or filtered for further processing. For example, after leaving the third washing tank 200" de-scaled activated carbon-gold particulate may be separated from a caustic washing/fluidizing solution by a screening or filtering process. The strained particulate may then be added to a strip solution of water, caustic, and cyanide for use with downstream elution and electrowinning processes.

The washers 10, 210 shown and described, when used, may reduce or eliminate the need to continually purchase particulate and cleaning/rinsing agents. For example, in the area of precious metal recovery, washers 10, 210 may significantly reduce the need to continually purchase large quantities of acid, water, caustic, and carbon. Washers 10, 210 may also significantly reduce the amount of spent acid, water, caustic, and carbon requiring disposal thereby reducing the potential for environmental harm.

It should be known that the particular features and suggested uses of the washers 10, 210 described herein are exemplary in nature and should not limit the scope of the invention. For example, fluidized beds and/or portions thereof 21, 221 may be replaced with, or used in combination with one or more mechanical or forced air agitators (not shown) to suspend particulate 120. Moreover, the number of chambers 20, 30, 40; 220, 230, 240 per washer 10, 210 may be greater or less than what is shown. In some embodiments, the relative sizes, dimentions and/or volumes of chambers 20, 30, 40; 220, 230, 240 may vary. In other embodiments, the chambers 20, 30, 40; 220, 230, 240 may be dimensioned/proportioned similarly. Additionally, one or more portions of a washer 10, 210 may be placed in series or parallel with other washer components in order to increase throughput or tailor a washer to a specific process. For example, a third chamber 40 of a first washer 10 may be directly or indirectly coupled to a plurality of downstream washers 10 via multiple first inlets 22 and multiple first chambers 20. Alternatively, multiple washing tanks 200 may replace any one tank 200 in a washer 210 by simply splitting inlets 222, 223a, and/or outlets 223b, 227. Similarly, any one chamber 20, 30, 40 may be compartmentalized into multiple chambers.

A contractor or other entity may provide a system including a washer 10, 210 as shown and described. For instance, the contractor may receive a bid request for a project related to designing a system for washing a particulate, or the contractor may offer to design such a system.

The contractor may then provide a washer 10, 210, for example, one including any one or more of the features shown and/or described in the embodiments discussed above. The contractor may provide such devices by selling those devices or by offering to sell those devices. The contractor may provide various embodiments that are sized, shaped, and/or otherwise configured to meet the design criteria of a particular client or customer. The contractor may subcontract the fabrication, delivery, sale, or installation of a component of the devices or of other devices used to provide such devices. The contractor may also survey a site and design or designate one or more storage areas for stacking the material used to manufacture the devices. The contractor may also maintain, modify, or upgrade the provided devices. The contractor may provide such maintenance or modifications by subcontracting such services or by directly providing those services or components needed for said maintenance or modifications, and in some cases, the contractor may modify an existing system with a "retrofit kit" to arrive at a modified system comprising one or more features of the systems discussed herein.

Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. It is believed that while the invention is described to be particularly advantageous in washing activated carbon loaded with a precious metal to de-scale the activated carbon, it would also be useful in replacing virtually any type of washing process requiring sequential batch process steps. Alternatively, washers 10, 210 may be used to sequentially and continuously load activated carbon. For example, infeed particulate may comprise activated carbon and first, second, and third fluidization mediums may be a pregnant solution containing a dissolved precious metal. In some instances, washers 10, 210 described herein may have equivalent utility in other fields of endeavor, such as for washing or cooking edibles. For example, feed particulate 120 may comprise grain, the first fluidization medium may comprise cold water, and the second fluidization medium may comprise hot water. Accordingly, it is to be understood that the drawings and descriptions herein are preferred by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.

Reference numeral identifiers

10, 210 washer 50 mount

20, 220 first chamber 60 bottom surface

21, 221 first fluidized bed panel 62 back surface

22, 222 first inlet 64 front surface

23a, 223a first recirculation inlet 66 left side surface

23b, 223b first recirculation outlet 68 right side surface

24, 224 first weir 72 first baffle

25 first channel drain 74 second baffle

26, 226 first screen 76 third baffle

27, 227 first overflow outlet 82, 282 first channel

28 first opening 84, 284 second channel

28a aperture 86, 286 third channel

28b track 92 first divider

28c gate 94 second divider

28d threads 96 third divider

28e bearing 100 flow of entering particulate

28f gate block 102 flow of fluidized particulate and fluidization medium

28g threaded hole 104 extent of fluidization of particulate

28h wheel 106 extent of fluidization medium

28i bearing 108 overflow of fluidization medium

28j shaft 1 10 outflow of screened particulate

29, 229 first recirculation tank 1 12 outflow of drained fluidization medium

30, 230 second chamber 120 particulate

31, 231 second fluidized bed panel 130 first fluidization medium

32, 232 second inlet 200 washing tank

33a, 233a second recirculation inlet 200' washing tank

33b, 233b second recirculation outlet 200" washing tank

34, 234 second weir 228 first discharge outlet

35, 235 second channel drain 238 second discharge outlet

36, 236 second screen 248 third discharge outlet

37, 237 second overflow outlet 250 flow of entering particulate

38 second opening 251 overflow of first fluidization medium

39, 239 second recirculation tank 252 outflow of particulate and first fluidization medium

40, 240 third chamber 253 outflow of drained first fluidization medium

41, 241 third fluidized bed panel 254 overflow of second fluidization medium

42, 242 third inlet 255 outflow of particulate and second fluidization medium

43a, 243a third recirculation inlet 256 outflow of drained second fluidization medium

43b, 243b third recirculation outlet 257 overflow of third fluidization medium

44, 244 third weir 258 outflow of particulate and third fluidization medium

45, 245 third channel drain 260 bottom wall

46, 246 third screen 266 inner tubular wall

47, 247 third overflow outlet 268 outer tubular wall

48 third opening 1000 process of washing a particulate

49, 249 third recirculation tank 1002-1048 steps for washing a particulate