Classifier

Abstract

A classifier and a method of separating material using such a classifier are disclosed. The classifier comprises a mixing chamber having a mixing fluidization floor and a concentration chamber having a concentration fluidization floor. The concentration fluidization floor and at least a portion of the concentration chamber is located below the mixing fluidization floor. The method of separating material using such a classifier comprises delivering material to be separated into a mixing chamber of the classifier, fluidizing the material in the mixing chamber; transferring some of the material to a concentration chamber of the classifier in fluid communication with the mixing chamber, fluidizing the material in the concentration chamber, forming a concentrating fluidized bed in the concentration chamber, separating the material with at least the concentrating fluidized bed and drawing heavier portions of the separated material from the concentration chamber.

Claims

1. A classifier comprising: a mixing chamber having a mixing fluidization floor; and a concentration chamber having a concentration fluidization floor; wherein the concentration fluidization floor and at least a portion of the concentration chamber is located below the mixing fluidization floor; and wherein the concentration chamber, is substantially elongated and wherein the concentration chamber extends downward from an apex region of the mixing fluidization floor; and wherein the concentration chamber has a horizontal cross-sectional area that is 20 to 200 times smaller than the horizontal cross-sectional area of the mixing chamber.

2. The classifier of claim 1, wherein the concentration chamber, having an end adjacent to the mixing fluidization floor, is substantially elongated and the concentration fluidisation floor is located at an opposite end of the concentration chamber to the end located adjacent the mixing fluidisation floor.

3. The classifier of claim 1, wherein the concentration chamber has an outlet and at least two pressure sensors located longitudinally between the mixing fluidisation floor and the concentration fluidisation floor.

4. The classifier of claim 1 wherein a separation chamber is positioned above the mixing chamber.

5. The classifier of claim 4 wherein at least one launder is positioned within the separation chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein:

(2) FIG. 1 is a side perspective view of a classifier according to an embodiment of the invention;

(3) FIG. 2 is a cross-sectional view of FIG. 1;

(4) FIG. 3 is a side elevation cross-sectional view of the classifier illustrated in FIG. 1;

(5) FIG. 4 is a top plan cross-sectional view of the classifier illustrated in FIG. 1;

(6) FIG. 5 is a top perspective view of the classifier illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIGS. 1 to 5 illustrate a classifier in the form of a Reflux classifier 100 used to separate material on the basis of size and weight. The Reflux classifier 100 has a mixing chamber 120 located above a concentration chamber 140 and below a separation chamber in the form of a lamella chamber 160.

(8) As illustrated most clearly in FIGS. 2 and 3 which show cross-sectional views of the classifier 100, the mixing chamber 120 has a mixing fluidisation floor 122 and the concentration chamber 140 has a concentration fluidisation floor 142. The fluidisation floors 122 and 142 are both generally conical in shape with a plurality of nozzles 124 (not shown in concentration fluidisation floor 142).

(9) The concentration chamber 140 is located centrally at the apex of the mixing fluidisation floor 122 and extends downwardly below the mixing fluidisation floor 122 and mixing chamber 120 to the concentration fluidisation floor 142 and material outlet in the form of an underflow valve 144. The underflow valve 144 is in fluid communication with the concentration chamber 140 and can be actuated to selectively allow material to pass therethrough.

(10) The concentration chamber 140 is considerably smaller than the mixing chamber 120, most notably in cross-sectional area across the horizontal axis (i.e. perpendicularly to the force of gravity) as most clearly illustrated in FIG. 4. In preferred embodiments the horizontal cross-sectional area of the concentration chamber 140 is 20 to 200 times smaller than the horizontal cross-sectional area of the mixing chamber 120. The concentration fluidisation floor 142 is consequently also smaller than the mixing fluidisation floor 122.

(11) The concentration chamber 140 is elongate in the form of a cylinder with the mixing fluidisation floor 122 and the concentration fluidisation floor 142 located at adjacent ends along a longitudinal axis of the concentration chamber 140. Both the mixing fluidisation floor 122 and the concentration fluidisation floor 142 have central openings, with the mixing fluidisation floor 122 having the concentration chamber 140 located in its central opening and the concentration fluidisation floor 142 having the underflow valve 144 located in its central opening.

(12) The mixing chamber 120 has a fluidisation chamber 126 located below its fluidisation floor 122 and the concentration chamber 140 similarly has a fluidisation chamber 146 located below its fluidisation floor 142. The fluidisation chambers 126 and 146 are fluidly communicated to their respective mixing chamber 120 and concentration chamber 140 via their respective nozzles in the mixing fluidisation floor 122 and the concentration fluidisation floor 142.

(13) The lamella chamber 160, which is located directly above the mixing chamber 120, has an inlet 162 and an outlet 164. As seen most clearly in FIG. 5 which shows the classifier 100 with its top (not shown) removed, the lamella chamber 160 has a series of plate arrays 166. The plate arrays 166 have parallel plates that are inclined relative to the axis of gravity to provide a classifying effect to material that passes through the plate arrays 166.

(14) The inlet 162 is fluidly connected to a plurality of inlet chambers 168 which may have an inclined de-aeration ceiling 170 that urges lighter air particles upwards toward a de-aeration pipe 172. Each inlet chamber 168 is fluidly connected to the mixing chamber 120, via optional chutes 174 that extend into the mixing chamber 120, allowing slurry from the inlet chambers 168 to make its way to the mixing chamber 120 for processing.

(15) A plurality of launders 176 are provided in the lamella chamber 160 to catch particles located within the slurry after it has passed through the plate arrays 166. The launders 176 are fluidly connected to an outlet chamber 178 which is in turn fluidly connected to the outlet 164. The de-aeration pipes 172 which may be present are fluidly connected from the inlet chamber 168 directly to the launders 176 to allow lighter air particles to bypass the mixing chamber 120 and plate arrays 166.

(16) In use, the Reflux classifier 100 receives material to be separated as slurry into inlet 162 where it is processed by the Reflux classifier 100. Specifically, the material to be processed is passed from inlet 162 to inlet chamber 168 where it may be de-aerated as any air in the material rises and is urged toward de-aeration pipe 172, by inclined de-aeration ceiling 170 of the inlet chamber 168. The air passes through de-aeration pipe 172 to the launders 176.

(17) From the inlet chamber 168 the material then travels down chutes 174 to the mixing chamber 120 located below the lamella chamber 160. The majority of the slurry is then mixed and fluidised by the fluidising mixing fluidisation floor 122 of the mixing chamber 120 and a minority portion, typically comprising heavier portions of the material to be separated, passes to the concentration chamber 140 where it is fluidised by the concentration fluidisation floor 142.

(18) A concentrating fluidised bed is formed in the concentrating chamber 140 and a mixing fluidised bed is formed in the mixing chamber 120. Heavier materials are concentrated by the concentrating fluidised bed which, when appropriate, can be drawn from the underflow valve 144. The mixing fluidised bed assists in flushing light materials to overflow via lamella chamber 160 and outlet 164.

(19) Generally lighter materials pass upwardly through the lamella chamber 160 where any heavier particles are dropped into the mixing chamber 120 and/or the concentration chamber 140 by the parallel plates 166. The lighter and smaller particles are able to pass through the plates 166 where they pass into the launders 176, into the outlet chamber 178 and out of the outlet 164.

(20) Advantageously, the Reflux classifier 100 can effectively separate materials with low grades. The concentration chamber 140 can quickly and efficiently form a concentrating bed over its reduced surface area, relative to the mixing chamber 120. This not only enables fast operation with minimal time delay waiting for an adequate fluidised bed to form, but also provides a more efficient concentrating operation that yields a very high grade output, from the underflow valve 144, that requires minimal, if any, further processing. The Reflux classifier 100 therefore realises significant increase in productivity as well as a reduction in operating and capital costs.

(21) In this specification, adjectives such as first and second, left and right, top and bottom, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Where the context permits, reference to an integer or a component or step (or the like) is not to be interpreted as being limited to only one of that integer, component, or step, but rather could be one or more of that integer, component, or step etc.

(22) The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. The invention is intended to embrace all alternatives, modifications, and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

(23) In the present specification and claims (if any), the word comprising 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 unless the context of use indicates otherwise.